Process for producing thermoplastic resin molded product and thermoplastic resin particle composition

ABSTRACT

A process for producing a thermoplastic resin molded product, comprising: a placement step of placing a thermoplastic resin particle composition  6 A into a cavity  22  of a rubber die  2  made of a rubber material; a particle heating step of irradiating the thermoplastic resin particle composition  6 A in the cavity  22  with electromagnetic waves having wavelengths ranging from 0.78 to 2 μm through the rubber die  2 , thereby heating to melt the thermoplastic resin particle composition  6 A; a filling step of filling a thermoplastic resin  6  in a molten state into a space  220  left in the cavity  22 ; and a cooling step of cooling a thermoplastic resin  6  in the cavity  22  thereby obtaining a thermoplastic resin molded product.

TECHNICAL FIELD

The present invention relates to a process for producing a thermoplasticresin molded product, including filling a thermoplastic resin particlecomposition into a cavity of a rubber die to obtain the thermoplasticresin molded product, and a thermoplastic resin particle composition.

BACKGROUND ART

Resin molded products in specific shapes are made from thermoplasticresins by various common processes, such as injection molding, blowmolding, extrusion molding, and press molding.

Patent Document 1 discloses a process for obtaining a resin moldedproduct made of a thermoplastic resin by vacuum cast molding using arubber mold, wherein the thermoplastic resin is selectively heated inpreference to the mold. In the resin molding process, when thethermoplastic resin in a molten state is filled into the cavity of themold, the thermoplastic resin is irradiated with electromagnetic waveshaving wavelengths ranging from 0.78 to 2 μm through the mold, wherebythe thermoplastic resin is more strongly heated than the rubber mold,based on the difference of the physical properties of the rubbercomposing the mold and the thermoplastic resin.

However, when a thermoplastic resin is molded using a rubber mold,additional means may be necessary for improving the properties such asshape and surface accuracy of the resin molded product. In particular,when the resin molded product to be molded is large or thin-walled, orthe thermoplastic resin material used for molding has a high viscosity,mold cavity filling may be so difficult that it requires additionalmeans for improving the above-described properties.

Alternatively, for example, Patent Document 2 discloses a powder slashmolding process, including attaching a powder slash material in apowdery state to the faces of a die and melting it to an intendedthickness, and then cooling the material thereby molding a resin moldedproduct adhered to the die. However, Patent Document 2 includes nodescription about the problem to be solved by the present invention, orthe difficulty in increasing the filling pressure of a thermoplasticresin filled into a rubber mold, and thus includes no means forimproving the above-described properties.

Patent Document 1: Japanese Unexamined Patent Application PublicationNo. 2007-216447

Patent Document 2: Japanese Unexamined Patent Application PublicationNo. 2000-254930

DISCLOSURE OF INVENTION Problems to be Solved by the Invention

In view of the above problems, the present invention is intended toprovide a process for producing a thermoplastic resin molded productwhich effectively improves the properties, such as shape and surfaceaccuracy, of a thermoplastic resin molded product made from athermoplastic resin using a rubber die, and a thermoplastic resinparticle composition.

Means for Solving the Problems

A first aspect of the present invention is a process for producing athermoplastic resin molded product, including: a placement step ofplacing a thermoplastic resin particle composition into a cavity of arubber die made of a rubber material; a particle heating step ofirradiating the thermoplastic resin particle composition in the cavitywith electromagnetic waves having wavelengths ranging from 0.78 to 2 μmthrough the rubber die, thereby heating to melt the thermoplastic resinparticle composition; and a cooling step of cooling a thermoplasticresin in the cavity thereby obtaining a thermoplastic resin moldedproduct.

In the process of the present invention for producing a thermoplasticresin molded product, a thermoplastic resin particle composition is usedfor the molding of a thermoplastic resin molded product by filling athermoplastic resin into a rubber die.

Specifically, firstly, as the placement step, a thermoplastic resinparticle composition is placed in the cavity of the rubber die. At thattime, the thermoplastic resin particle composition may be filled intoalmost whole or part of the cavity.

Subsequently, as the particle heating step, the thermoplastic resinparticle composition in the cavity is irradiated with electromagneticwaves having wavelengths ranging from 0.78 to 2 μm through a rubber die.At that time, the thermoplastic resin particle composition isselectively heated (the thermoplastic resin particle composition is morestrongly heated) in preference to the rubber die, based on thedifference of the physical properties of the rubber material composingthe rubber die and the thermoplastic resin particle composition in apowdery state. As a result of this, the thermoplastic resin particlecomposition is melted with the temperature rise of the rubber diesuppressed.

In addition, the thermoplastic resin is filled into the whole of thecavity without increasing the filling pressure so high, whereby thedeformation and opening of the rubber die are effectively prevented.Therefore, resin leakage at the parting surface in the rubber die isprevented, and the thermoplastic resin molded product obtained throughthe cooling step has effectively improved properties such as shape andsurface accuracy.

Therefore, according to the above-mentioned process for producing athermoplastic resin molded product, when a thermoplastic resin is moldedusing a rubber die, the thermoplastic resin molded product haseffectively improved properties such as shape and surface accuracy. Inaddition, the present invention is markedly effective when thethermoplastic resin molded product to be molded is large or thin-walled,or when the thermoplastic resin used for molding has a high viscosity.

A second aspect of the present invention is a thermoplastic resin moldedproduct obtained by the process of the first aspect for producing athermoplastic resin molded product.

The thermoplastic resin molded product of the present invention isproduced (molded) using the thermoplastic resin particle composition ofthe first invention.

Therefore, the thermoplastic resin molded product of the presentinvention has effectively improved properties such as shape and surfaceaccuracy.

A third aspect of the present invention is a thermoplastic resinparticle composition to be filled into a cavity of a rubber die made ofa rubber material, and heated to be melted by irradiation withelectromagnetic waves having wavelengths ranging from 0.78 to 2 μmthrough the rubber die, the thermoplastic resin particle compositionhaving a bulk density of 0.4 g/cm³ or more.

The thermoplastic resin particle composition of the present inventionprevents development of a defect such as burning caused by excessiverate of heating by the electromagnetic waves having wavelengths rangingfrom 0.78 to 2 μm.

Therefore, the thermoplastic resin particle composition of the presentinvention gives a thermoplastic resin molded product having goodproperties such as shape and surface accuracy.

When the thermoplastic resin particle composition has a small particlesize, the bulk density likely decreases. If the particle size of thethermoplastic resin particle composition is so small that the bulkdensity falls short of 0.4 g/cm³, a defect such as burning may develop.

The thermoplastic resin particle composition may have almost uniformparticle sizes, or may be a mixture of particles having differentaverage particle sizes or of different particle size classes.

The thermoplastic resin particle composition is preferably composed ofalmost spherical particles thereby increasing the bulk density.

The bulk density of the thermoplastic resin particle composition islikely inversely proportional to the temperature rise rate of thethermoplastic resin irradiated with the electromagnetic wave. It islikely that the smaller the bulk density, the higher the temperaturerise rate, and the higher the bulk density is, the smaller thetemperature rise rate is. Therefore, if the bulk density is less than0.4 g/cm³, the temperature rise rate is so high that the thermoplasticresin particle composition may develop a defect such as burning.Specifically, the thermoplastic resin particle composition may be burnedat the side irradiated with the electromagnetic wave. On the other hand,if the temperature rise rate is so low, the time of irradiation with theelectromagnetic waves must be prolonged, which may be result in a defectsuch as burning in the rubber die. Therefore, the bulk density of thethermoplastic resin particle composition may be 0.8 g/cm³ or less.

A fourth aspect of the present invention is a thermoplastic resinparticle composition to be filled into a cavity of a rubber die made ofa rubber material, and heated to be melted by irradiation withelectromagnetic waves having wavelengths ranging from 0.78 to 2 μmthrough the rubber die, the thermoplastic resin particle compositionbeing composed of 0.1 to 20% by mass of small thermoplastic resinparticles having a particle size of 1 to 100 μm, the balance being largethermoplastic resin particles larger than the small thermoplastic resinparticles.

The thermoplastic resin particle composition of the present invention ishighly useful in producing a thermoplastic resin molded product formedby electromagnetic wave irradiation through a rubber die.

Specifically, the thermoplastic resin particle composition of thepresent invention is composed of small thermoplastic resin particleshaving a particle size of 1 to 100 μm, and large thermoplastic resinparticles larger than the small particles. As a result of this, when thethermoplastic resin particles are filled into the cavity of a rubberdie, the small thermoplastic resin particles adhere to the inner wallsurface of the cavity, and the large thermoplastic resin particles passon the inner side of the small thermoplastic resin particles in thecavity. Therefore, the thermoplastic resin particles are smoothly filledinto the cavity.

The rubber die of the present invention is made of a rubber material,and the small thermoplastic resin particles have a particle size in arange from 1 to 100 μm. As a result of this, the particles adhere to theinner wall surface of the cavity made of a rubber material.

The proportions of the small and large thermoplastic resin particles is0.1 to 20% by mass and 80 to 99.9% by mass, respectively. The proportionof the large thermoplastic resin particles is so large that developmentof a defect such as burning in the thermoplastic resin particlecomposition is prevented during heating to melt the thermoplastic resinparticle composition by irradiation with the electromagnetic wavesthrough a rubber die.

In addition, the thermoplastic resin particle composition filled intothe cavity is heated to be melted by irradiation with theelectromagnetic waves through a rubber die, and then the thermoplasticresin in the cavity is cooled to obtain a thermoplastic resin moldedproduct. After the thermoplastic resin particle composition is heated tobe melted in the cavity, as necessary, a thermoplastic resin in a moltenstate may be filled (replenished) into the space left in the cavityafter the heating and melting.

Therefore, the thermoplastic resin particle composition of the presentinvention used for molding by electromagnetic wave irradiation allowssmooth filling of the thermoplastic resin particles into the cavity, andprevents development of a defect such as burning, thereby producing athermoplastic resin molded product having good properties such asappearance, shape, and surface accuracy, and high mechanical strength.The present invention is markedly effective when the thermoplastic resinmolded product to be molded is large or thin-walled, or when thethermoplastic resin particles used for molding has a high viscosity.

If the small thermoplastic resin particles has a particle size of lessthan 1 μm, its production is difficult, and they are hard to handleduring molding of the thermoplastic resin molded product. On the otherhand, if the particle size of the small thermoplastic resin particles ismore than 100 μm, adhesion of the small thermoplastic resin particles tothe inner wall surface of the cavity is difficult.

If the proportion of the small thermoplastic resin particles is lessthan 0.1% by mass, the amount of the small thermoplastic resin particlesto be adhered to the inner wall surface of the cavity is so small thatthe passage of the large thermoplastic resin particles on the inner sideof the small thermoplastic resin particles in the cavity is difficult.On the other hand, if the proportion of the small thermoplastic resinparticles is more than 20% by mass, during heating to melt thethermoplastic resin particle composition, the small thermoplastic resinparticles adhered to the inner wall surface of the cavity may develop adefect such as burning.

The particle size of the small thermoplastic resin particles is morepreferably from 3 to 90 μm. The particle size of the large thermoplasticresin particles may be, for example, from 200 to 3000 μm. The particlesize of the large thermoplastic resin particles is more preferably from300 to 2000 μm, and even more preferably from 350 to 1500 μm.

The proportion of the small thermoplastic resin particles in thethermoplastic resin particle composition is preferably 10% by mass orless, and more preferably 7% by mass or less.

The melt flow rate of the thermoplastic resin contained in the small andlarge thermoplastic resin particles (220° C., 10 kg load) is preferablyfrom 1 to 100 g/10 min, more preferably from 5 to 80 g/10 min, and evenmore preferably from 15 to 65 g/10 min.

The large and small thermoplastic resin particles may be composed ofidentical thermoplastic resins having the same constitution.Alternatively, the large and small thermoplastic resin particles may becomposed of different thermoplastic resins having differentconstitutions. In this case, the thermoplastic resins are preferablyhighly compatible with each other, thereby increasing the mechanicalstrength.

A fifth aspect of the present invention is a thermoplastic resinparticle composition to be filled into the cavity of a rubber die madeof a rubber material, and heated to be melted by irradiation withelectromagnetic waves having wavelengths ranging from 0.78 to 2 μmthrough the rubber die, the thermoplastic resin particle compositioncontaining thermoplastic resin particles and fine particles at least oneof an inorganic powder and a lubricant, the thermoplastic resinparticles having a number average particle size of 200 to 3000 μm, thefine particles having a volume average particle size of 0.5 to 50 μm,and the content of the fine particles being from 0.1 to 10 parts by masswith reference to 100 parts by mass of the thermoplastic resinparticles.

The thermoplastic resin particle composition of the present invention ishighly useful in producing a thermoplastic resin molded product formedby electromagnetic wave irradiation through a rubber die.

Specifically, the thermoplastic resin particle composition of thepresent invention contains thermoplastic resin particles having a numberaverage particle size of 200 to 3000 μm and fine particles (at least oneof an inorganic powder and a lubricant) having a volume average particlesize of 0.5 to 50 μm. As a result of this, when the thermoplastic resinparticles are filled into the cavity of a rubber die, the fine particlesadhere to the inner wall surface of the cavity, and the thermoplasticresin particles pass on the inner side of the fine particles in thecavity. On that account, the thermoplastic resin particles are smoothlyfilled into the cavity.

The rubber die of the present invention is made of a rubber material,and the fine particles has a volume average particle size of 0.5 to 50μm, thereby allowing adhesion of the fine particles to the inner wallsurface of the cavity made of a rubber material.

The proportion of the thermoplastic resin particles to the fineparticles is 100 parts by mass to 0.1 to 10 parts by mass. As a resultof this, the proportion of the thermoplastic resin particles is so highthat the thermoplastic resin particle composition will not develop adefect such as burning during heating and melting by irradiation withelectromagnetic waves through a rubber die.

The thermoplastic resin particle composition filled into the cavity isheated to be melted by irradiation with the electromagnetic wavesthrough the rubber die, and then the thermoplastic resin in the cavityis cooled to obtain a thermoplastic resin molded product. After thethermoplastic resin particle composition is heated to be melted in thecavity, as necessary, a thermoplastic resin in a molten state may befilled (replenished) into the space left in the cavity after thermal andmelting.

Therefore, the thermoplastic resin particle composition of the presentinvention used for molding by electromagnetic wave irradiation allowssmooth filling of the thermoplastic resin particles into the cavity, andprevents development of a defect such as burning, thereby producing athermoplastic resin molded product having good properties such asappearance, shape, and surface accuracy, and high mechanical strength.The present invention is markedly effective when the thermoplastic resinmolded product to be molded is large or thin-walled, or when thethermoplastic resin particles used for molding has a high viscosity.

The volume average particle size of the fine particles refers to themedian particle size of the volume-weighted particle size, or 50%average particle size (“D₅₀”) measured by laser diffractometry or othermethod.

The content of the fine particles is more preferably from 0.2 to 8 partsby mass, and even more preferably from 0.5 to 5 parts by mass withreference to 100 parts by mass of the thermoplastic resin particles. Thecontent of the fine particles is even more preferably 3 parts by mass orless.

When the fine particles is composed solely of the inorganic powder, theamount of the inorganic powder is more preferably from 0.2 to 8 parts bymass, and even more preferably from 0.5 to 5 parts by mass withreference to 100 parts by mass of the thermoplastic resin particles.When the fine particles is composed solely of the lubricant, the amountof the lubricant is more preferably from 0.2 to 8 parts by mass, andeven more preferably from 0.5 to 5 parts by mass with reference to 100parts by mass of the thermoplastic resin particles.

A sixth aspect of the present invention is a thermoplastic resinparticle composition to be filled into the cavity of a rubber die madeof a rubber material, and heated to be melted by irradiation withelectromagnetic waves having wavelengths ranging from 0.78 to 2 μmthrough the rubber die, the thermoplastic resin particle compositioncontaining 0.0005 to 0.1 parts by mass of an infrared ray absorbingagent with reference to 100 parts by mass of the thermoplastic resinparticles.

The thermoplastic resin composition of the present invention is highlyuseful in molding by electromagnetic wave irradiation (molding of athermoplastic resin by irradiation with electromagnetic waves through arubber die).

Specifically, the thermoplastic resin composition of the presentinvention contains 0.0005 to 0.1 parts by mass of an infrared rayabsorbing agent with reference to 100 parts by mass of the thermoplasticresin. When the thermoplastic resin composition is filled into thecavity of the rubber die, and the thermoplastic resin composition isirradiated with electromagnetic waves having wavelengths ranging from0.78 to 2 μm through a rubber die, the infrared ray absorbing agenteffectively absorbs the electromagnetic wave.

As a result of this, even if the thermoplastic resin is transparent orhas a white or any other color, the thermoplastic resin compositioneffectively absorbs the electromagnetic waves to be heated and meltedquickly. In addition, the rubber die used for molding is readily made,which allows low-cost production of the thermoplastic resin moldedproducts of various shapes.

Therefore, the thermoplastic resin particle composition of the presentinvention offers a thermoplastic resin molded product having goodproperties such as shape and surface accuracy.

The amount of the infrared ray absorbing agent is preferably from 0.001to 0.08 parts by weight, and even more preferably from 0.005 to 0.06parts by weight with reference to 100 parts by mass of the thermoplasticresin. When the amount is 0.0005 parts by weight or more, the timenecessary for heating to melt the thermoplastic resin composition byirradiation with electromagnetic waves is further reduced. The infraredray absorbing agent may be used alone or in combination of two or morekinds thereof.

The use of the infrared ray absorbing agent facilitates the molding of athermoplastic resin molded product having a haze value of 20% or less.

The haze value is determined by measuring a test piece having athickness of 2.5 mm in accordance with JIS K7136. The smaller the hazevalue is, the higher transparency is. When the thermoplastic resincomposition is formed into a thermoplastic resin molded product, thehaze value is preferably 15% or less, even more preferably 10% or less,and particularly preferably 8% or less. The haze value can be minimizedto almost 0% by reducing the amount of the infrared ray absorbing agent.

The use of the infrared ray absorbing agent facilitates the molding of athermoplastic resin molded product having a whiteness value of 30% ormore.

The whiteness value W(%) is calculated by the formula:

W(%)=100−{(100−L)² +a ² +b ²}^(1/2)

wherein L represents brightness, a represents redness, b representsyellowness measured using a Hunter color-difference meter. The higherthe whiteness value is, the closer to white the resin is.

When the thermoplastic resin composition is formed into a thermoplasticresin molded product, the whiteness value is preferably 40% or more,even more preferably 50% or more, and particularly preferably 70% ormore. The whiteness value can be maximized to almost 100%.

The whiteness value may be adjusted by appropriately selecting the typeand content of the thermoplastic resin, infrared ray absorbing agent,and coloring agent.

If the content of the infrared ray absorbing agent is less than 0.0005parts by mass with reference to 100 parts by mass of the thermoplasticresin, the amount of the infrared ray absorbing agent is so small thatthe thermoplastic resin composition cannot sufficiently absorbelectromagnetic waves. On the other hand, if the content of the infraredray absorbing agent is more than 0.1 parts by mass with reference to 100parts by mass of the thermoplastic resin, the excessive amount of theinfrared ray absorbing agent makes it difficult to keep a whitenessvalue of the thermoplastic resin molded product at 30% or more.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of the state after the placement step of theprocess for producing a thermoplastic resin molded product in Example 1.

FIG. 2 is an illustration of the state during the particle heating stepand the vacuum step of the process for producing a thermoplastic resinmolded product in Example 1.

FIG. 3 is an illustration of the state after the filling step of theprocess for producing a thermoplastic resin molded product in Example 1.

FIG. 4 shows graphs of the optical transmittance in the transparent andtranslucent silicone rubbers in Example 1, taking the wavelength (nm) asabscissa, and the optical transmittance (%) as ordinate.

FIG. 5 shows graphs of the bulk density (g/cm³) and the angle of repose(°) of the particle samples in Example 1.

FIG. 6 shows a graph illustrating the relationship between the bulkdensity (g/cm³) and the temperature rise rate (° C./sec) of the particlesamples in Example 1.

FIG. 7 shows a state of filling the small and large thermoplastic resinparticles into the cavity of the rubber die in Example 2.

FIG. 8 shows a state of filling the large thermoplastic resin particlesalone into the cavity of the rubber die in Example 2.

FIG. 9 shows graphs of the optical absorption coefficient (%) of thethermoplastic resins free of or containing an infrared ray absorbingagent in Example 4, taking the wavelength (nm) as abscissa, and theoptical absorption coefficient (%) as ordinate.

FIG. 10 shows graphs of the optical absorption coefficient (%) of thethermoplastic resins free of or containing an infrared ray absorbingagent in Example 5, taking the wavelength (nm) as abscissa, and theoptical absorption coefficient (%) as ordinate.

BEST MODE FOR CARRYING OUT THE INVENTION

Preferred embodiments of the present invention are described below.

In the first to sixth aspects of the present invention, thethermoplastic resin particle composition refers to a wide range ofparticles ranging from, for example, fine particles (powder) having anaverage particle size of several hundreds of micrometers to particleshaving an average particle size of several millimeters.

The reason why the electromagnetic waves having wavelengths ranging from0.78 to 2 μm selectively heat the thermoplastic resin in preference tothe rubber die is considered as follows.

The electromagnetic waves having wavelengths ranging from 0.78 to 2 μmirradiated to the surface of the rubber die likely transmits the rubberdie and are adsorbed into the thermoplastic resin, rather than beingabsorbed into the rubber die. Therefore, the optical energy of theelectromagnetic waves having wavelengths ranging from 0.78 to 2 μm arelikely preferentially absorbed into the thermoplastic resin toselectively heat the thermoplastic resin.

The electromagnetic waves irradiated to the thermoplastic resin throughthe rubber die may include waves having wavelengths outside the rangefrom 0.78 to 2 μm. In the electromagnetic waves or the transmittedelectromagnetic waves irradiated to the thermoplastic resin through arubber die, the proportion of the electromagnetic waves havingwavelengths ranging from 0.78 to 2 μm is preferably higher than that ofthe waves having wavelengths outside the range.

The reason why the electromagnetic waves having wavelengths ranging from0.78 to 2 μm is used for heating the thermoplastic resin is that theelectromagnetic waves in the wavelength range readily transmit throughthe rubber die, and are readily absorbed into the thermoplastic resin.

The electromagnetic waves preferably have a peak intensity in thewavelength range from 0.78 to 2 μm. In this case, the electromagneticwave generation source such as an electromagnetic wave generation meansmay be a halogen heater or infrared lamp which emits electromagneticwaves having wavelengths with specific distribution characteristics.

The rubber die may be made from transparent or translucent siliconerubber as a rubber material. The hardness of the silicone rubber may befrom 25 to 80 as measured according to the JIS-A standard.

The thermoplastic resin particles (including the large and smallthermoplastic resin particles) may be produced by any method such asmechanical grinding (room temperature or cold grinding, wet grinding,jet grinding), spraying (dry spraying, spray solidification), forcedemulsification (melt emulsification, solution emulsification),suspension polymerization, or emulsion polymerization.

For example, the thermoplastic resin particles may be those produced bycold grinding of thermoplastic resin pellets obtained with an extruder.The cold grinding process produces thermoplastic resin particles ofvarious particle sizes. The thermoplastic resin particles may beproduced by a so-called under water cut system using an extruderequipped at the tip thereof a dice having a small diameter. In the underwater cut system, particles (thermoplastic resin particles) of about 0.5mm are readily produced at a low cost.

The thermoplastic resin particles may be subjected to, as necessary,classification or screening.

The thermoplastic resin used in the thermoplastic resin particlecomposition may be selected from those absorbing electromagnetic waveshaving wavelengths ranging from 0.78 to 2 μm, thereby acceleratingheating.

The thermoplastic resin used in the thermoplastic resin particlecomposition is not particularly specified as long as it contains athermoplastic polymer, and examples thereof include rubber-reinforcedstyrene resins such as ABS resins (acrylonitrile-butadiene-styreneresins), ASA resins (acrylate-styrene-acrylonitrile resins), AES resins(acrylonitrile-ethylene-propylene-diene-styrene resins); styrene resinssuch as polystyrene, styrene-acrylonitrile copolymers, styrene-maleicanhydride copolymers, and (meth)acrylate ester-styrene copolymers;olefin resins such as polyethylene and polypropylene; acrylic resins,polycarbonate resins, polyester resins, polyamide resins, vinyl chlorideresins, polyarylate resins, polyacetal resins, polyphenylene etherresins, polyphenylene sulfide resins, fluorocarbon resins, imide resins,ketone resins, sulfone resins, urethane resins, polyvinyl acetates,polyethylene oxides, polyvinyl alcohols, polyvinyl ethers, polyvinylbutyrals, phenoxy resins, photosensitive resins, liquid crystallinepolymers, and biodegradable plastics. They may be used alone or incombination of two or more thereof.

Among the above thermoplastic resins, those preferred for the molding ofthe molded product include rubber-reinforced styrene resins, olefinresins, acrylic resins, polyester resins, polyamide resins, alloys ofpolyester resins and polycarbonate resins, alloys of rubber-reinforcedstyrene resins and polycarbonate resins, and alloys of rubber-reinforcedstyrene resins and polyester resins.

The thermoplastic resin particle composition is preferably arubber-reinforced styrene resin.

In this case, the thermoplastic resin molded product has more markedlyimproved properties such as shape and surface accuracy.

The rubber-reinforced styrene resin may be a rubber-reinforced styreneresin (A1) obtained by polymerizing a vinyl monomer (a2) composed of aaromatic monovinyl compound in the presence of a rubbery polymer (a1),or a mixture of the rubber-reinforced styrene resin (A1) and a(co)polymer (A2) composed of structural units derived from a vinylmonomer.

The rubbery polymer (a1) may be a homopolymer or copolymer as long as itis rubbery at room temperature, and is preferably a diene polymer (dienerubbery polymer) or a non-diene polymer (non-diene rubbery polymer). Therubbery polymer (a1) may be a crosslinked or non-crosslinked polymer.They may be used alone or in combination of two or more thereof.

Examples of the diene polymer include homopolymers such aspolybutadiene, polyisoprene, and polychloroprene; styrene-butadienecopolymer rubbers such as styrene-butadiene copolymers,styrene-butadiene-styrene copolymers, acrylonitrile-butadienecopolymers, and acrylonitrile-styrene-butadiene copolymers;styrene-isoprene copolymer rubbers such as styrene-isoprene copolymers,styrene-isoprene-styrene copolymers, and acrylonitrile-styrene-isoprenecopolymers; and natural rubbers. These copolymers may be block or randomcopolymers. These copolymers may be hydrogenated at a degree ofhydrogenation of less than 50%. The diene polymer may be used alone orin combination of two or more thereof.

Examples of the non-diene polymer include ethylene-α-olefin copolymerrubbers containing ethylene units and α-olefin units having 3 or morecarbon atoms, urethane rubbers, acrylic rubbers, silicone rubbers,silicon-acryl IPN rubbers, and polymers prepared by hydrogenation of(co)polymers containing units composed of a conjugated diene compound.These copolymers may be block copolymers or random copolymers. Thesecopolymers may be hydrogenated at a degree of hydrogenation of 50% ormore. The non-diene polymer may be used alone or in combination of twoor more thereof.

When the rubbery polymer (a1) is a diene polymer, the resin containingthe resultant rubber-reinforced styrene resin (A1) is generally referredto as “ABS resin”. When the rubbery polymer (a1) is composed at leastone of an ethylene-α-olefin and an ethylene-α-olefin-nonconjugated dienecopolymer, the resin containing the resultant rubber-reinforced styreneresin (A1) is generally referred to as “AES resin”. When the rubberypolymer (a1) is an acrylic rubber, the resin containing the resultantrubber-reinforced styrene resin (A1) is generally referred to as “ASAresin”.

The vinyl monomer (a2) used for the formation of the rubber-reinforcedstyrene resin (A1) may be composed solely of an aromatic vinyl compound,or a mixture of the aromatic vinyl compound with one or more compoundscopolymerizable with the aromatic vinyl compound, such as vinylcyanidecompounds, (meth)acrylate ester compounds, maleimide compounds, or acidanhydrides.

Accordingly, the vinyl monomer (a2) may be composed of one or morearomatic vinyl compounds, or a monomer composed of one or more aromaticvinyl compounds and one or more compounds copolymerizable with thearomatic vinyl compounds.

The aromatic vinyl compound is not particularly specified as long as itcontains at least one vinyl bond and at least one aromatic ring.Examples of the aromatic vinyl compound include styrene,α-methylstyrene, o-methylstyrene, p-methylstyrene, vinyltoluene,β-methylstyrene, ethyl styrene, p-tert-butyl styrene, vinyl xylene,vinylnaphthalene, monochlorostyrene, dichlorostyrene, monobromostyrene,dibromostyrene, and fluorostyrene. They may be used alone or incombination of two or more thereof. Among them, styrene andα-methylstyrene are preferred.

Examples of the vinylcyanide compound include acrylonitrile andmethacrylonitrile. Among them, acrylonitrile is preferred. They may beused alone or in combination of two or more thereof.

Examples of the (meth)acrylate ester compound include methylmethacrylate, ethyl methacrylate, n-propyl methacrylate, isopropylmethacrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butylmethacrylate, methyl acrylate, ethyl acrylate, n-propyl acrylate,isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, and tert-butylacrylate. They may be used alone or in combination of two or morethereof.

Examples of the maleimide compound include maleimide, N-methylmaleimide,N-butyl maleimide, N-phenyl maleimide, N-(2-methylphenyl)maleimide,N-(4-hydroxyphenyl)maleimide, and N-cyclohexyl maleimide. They may beused alone or in combination of two or more thereof. The introduction ofthe units of a maleimide compound may be achieved by, for example,copolymerizing a maleic anhydride, and then imidizing the copolymer.

Examples of the acid anhydride include maleic anhydride, itaconic acidanhydride, and citraconic acid anhydride. They may be used alone or incombination of two or more thereof.

In addition to the above compounds, as necessary, vinyl compounds havinga functional group such as a hydroxyl group, an amino group, an epoxygroup, an amide group, a carboxyl group, or an oxazoline group, may beused. Examples of the vinyl compounds include 2-hydroxyethylmethacrylate, 2-hydroxyethyl acrylate, hydroxystyrene,N,N-dimethylaminomethyl methacrylate, N,N-dimethylaminomethyl acrylate,N,N-diethyl-p-amino methylstyrene, glycidyl methacrylate, glycidylacrylate, 3,4-oxycyclohexyl methacrylate, 3,4-oxy cyclohexyl acrylate,vinyl glycidyl ether, glycidyl ether metharylate, allyl glycidyl ether,methacrylamide, acrylamide, methacrylic acid, acrylic acid, and vinyloxazoline. They may be used alone or in combination of two or morethereof.

As described above, when the thermoplastic resin is a rubber-reinforcedstyrene resin, the rubber-reinforced styrene resin may be composedsolely of the rubber-reinforced styrene resin (A1), or a mixture of therubber-reinforced styrene resin (A1) and the (co)polymer (A2) obtainedby polymerization of vinyl monomers. The vinyl monomers may be at leastone compound selected from the compounds used for the formation of therubber-reinforced styrene resin (A1), that is, aromatic vinyl compounds,vinylcyanide compounds, (meth)acrylate ester compounds, maleimidecompounds, acid anhydrides, and compounds having a functional group.Accordingly, the (co)polymer (A2) may be obtained by polymerization ofcomponents having the same constitution with the vinyl monomer (a2) usedfor the formation of the rubber-reinforced styrene resin (A1), monomersof the same type having different constitutions, or monomers ofdifferent types having different constitutions. Two or more of thesepolymers may be contained.

The graft rate of the rubber-reinforced styrene resin (A1) is preferablyfrom 30 to 150% by mass, and more preferably from 50 to 120% by mass. Ifthe graft rate of the rubber-reinforced styrene resin (A1) is too small,the thermoplastic resin molded product may have insufficient surfaceappearance and impact resistance. If the graft rate is too high, moldingprocessability deteriorates.

The graft rate is calculated by the formula:

graft rate (% by mass)={(y−x)/x}×100

wherein x is the gram of the rubber component in 1 gram of therubber-reinforced styrene resin (A1), and y is the gram of the insolublecomponent left after dissolving 1 g of the rubber-reinforced styreneresin (A1) in acetone (or acetonitrile when the rubbery polymer (a1) isan acrylic rubber).

The limiting viscosity [η] (measured in methyl ethyl ketone at 30° C.)of the soluble component of the rubber-reinforced styrene resin (A1) inacetone (or acetonitrile when the rubbery polymer (a1) is an acrylicrubber) is preferably from 0.2 to 1 dl/g, and more preferably from 0.3to 0.8 dl/g. When the limiting viscosity is within the range, thethermoplastic resin molded product offers good molding processabilityand the molded product has good impact resistance.

The graft rate and limiting viscosity [η] are readily controlled bychanging the type and amount of the polymerization initiator, chaintransferring agent, emulsifier, and solvent, and the time andtemperature of polymerization in the production of the rubber-reinforcedstyrene resin (A1).

Examples of the (co)polymer (A2) include the following (1) to (6). Therespective monomers may be the compounds used for the formation of therubber-reinforced styrene resin (A1), and preferred examples of thecompound are the same: (1) one or more (co)polymers obtained bypolymerization of an aromatic vinyl compound alone; (2) one or more(co)polymers obtained by polymerization of a (meth)acrylate estercompound alone; (3) one or more copolymers obtained by polymerization ofan aromatic vinyl compound and a vinylcyanide compound; (4) one or morecopolymers obtained by polymerization of an aromatic vinyl compound anda (meth)acrylate ester compound; (5) one or more copolymers obtained bypolymerization of an aromatic vinyl compound, a vinylcyanide compound,and other compound; (6) one or more copolymers obtained bypolymerization of an aromatic vinyl compound and a compound other than avinylcyanide compound.

They may be used alone or in combination of two or more thereof.

Accordingly, specific examples of the (co)polymer (A2) includeacrylonitrile-styrene copolymers, acrylonitrile-α-methylstyrenecopolymers, acrylonitrile-styrene-methyl methacrylate copolymers,styrene-methyl methacrylate copolymers, andacrylonitrile-styrene-N-phenyl maleimide copolymers.

The limiting viscosity [η] (measured in methyl ethyl ketone at 30° C.)of the (co)polymer (A2) is preferably from 0.2 to 0.8 dl/g. When thelimiting viscosity [η] is within the range, good physical propertybalance is attained between molding processability and impactresistance. The limiting viscosity [η] of the (co)polymer (A2) iscontrollable by adjusting the production conditions as in the case ofthe rubber-reinforced styrene resin (A1).

The limiting viscosity [η] (measured in methyl ethyl ketone at 30° C.)of the soluble component of the rubber reinforcement resin in acetone(or acetonitrile when the rubbery polymer (a1) is an acrylic rubber) ispreferably from 0.2 to 0.8 dl/g. When the limiting viscosity [η] iswithin the range, good physical property balance is attained betweenmolding processability and impact resistance.

Examples of the styrene resin include polymers obtained by polymerizingan aromatic vinyl compound alone, and copolymers obtained bycopolymerizing the aromatic vinyl compound with a compoundcopolymerizable with the aromatic vinyl compound, which are listed aboveas the examples of the (co)polymer (A2).

The olefin resin is not particularly specified as long as it is apolymer containing an α-olefin monomer unit having 2 or more carbonatoms. The olefin resin is preferably a polymer containing an α-olefinmonomer unit having 2 to 10 carbon atoms. Accordingly, examples of theolefin resin include (co)polymers composed mainly of one or moreα-olefin monomer units having 2 to 10 carbon atoms, and copolymerscomposed of one or more α-olefin monomer units having 2 to 10 carbonatoms and one or more monomer units of a compound copolymerizable withthe α-olefin. They may be used alone or in combination of two or morethereof.

Examples of the olefin resin include polyethylene, polypropylene,ethylene-propylene copolymers, polybutene-1, ethylene-butene-1copolymers. Among them, polyethylene, polypropylene, andpropylene-ethylene copolymers are preferred, and more preferred arepolymers containing 50% by mass or more of propylene units withreference to the whole monomer units, that is, polypropylene andethylene-propylene copolymers. The ethylene-propylene copolymers may berandom or block copolymers.

The olefin resin may be crystalline or non-crystalline. The olefin resinpreferably has a degree of crystallinity of 20% or more as measured byX-ray diffraction at room temperature.

The melting point of the olefin resin is preferably 40° C. or more basedon JIS K7121.

The molecular weight of the olefin resin is not particularly specified.From the viewpoint of moldability, the melt flow rate (measuredaccording to JISK7210: 1999, 230° C., load 2.16 kg) of the polypropyleneresin is usually from 0.01 to 500 g/10 minutes, more preferably 0.04,even more preferably 0.05 to 100 g/10 minutes, and the melt flow rate(measured according to JISK6922-2, 190° C., load 2.16 kg) of thepolyethylene resin is usually from 0.01 to 500 g/10 minutes, and morepreferably from 0.05 to 100 g/10 minutes.

The olefin resin may be an ionomer, an ethylene-vinyl acetate copolymer,an ethylene-vinyl alcohol copolymer, a cyclic olefin copolymer, or achlorinated polyethylene.

The acrylic resin may be obtain by polymerizing a (meth)acrylate estercompound alone, or copolymerizing a (meth)acrylate ester compound with avinyl monomer copolymerizable with the (meth)acrylate ester compound.Specific examples of the acrylic resin include homopolymers of methylmethacrylate, and copolymers of methyl methacrylate with an alkyl(meth)acrylate ester such as methyl acrylate, ethyl (meth)acrylate,propyl (meth)acrylate, butyl (meth)acrylate, or 2-ethylhexyl(meth)acrylate, or an aromatic vinyl monomer such as styrene,α-methylstyrene, or vinyltoluene. The term “(meth)acrylate ester” refersto an acrylate and/or a methacrylate.

The weight average molecular weight of the acrylic resin is preferablyfrom 50,000 to 400,000 as measured by the GPC method usingtetrahydrofuran as the solvent. When the weight average molecular weightis within the range, good molding processability is achieved, and theresultant transparent thermoplastic resin molded product has high impactresistance and toughness.

The acrylic resin may be composed of two or more acrylic resins havingdifferent weight average molecular weights, as long as the weightaverage molecular weight of the whole resin falls within the aboverange. The acrylic resin may be produced by a known polymerizationmethod such as radical polymerization, charge transfer radicalpolymerization, anionic polymerization, group transfer polymerization,or coordinated anionic polymerization.

The polycarbonate resin is not particularly specified as long as itcontains a carbonate bond in the main chain, and may be an aromatic oraliphatic polycarbonate. These polycarbonates may be used incombination. In the present invention, from the viewpoints of impactresistance and heat resistance, the polycarbonate resin is preferably anaromatic polycarbonate. The ends of the polycarbonate resin may bemodified by R—CO— or R′—O—CO— groups (R and R′ represent organicgroups). The polycarbonate resin may be used alone or in combination oftwo or more thereof.

The viscosity average molecular weight of the polycarbonate resin ispreferably from 12,000 to 40,000, as converted from the solutionviscosity measured at 20° C. using methylene chloride as the solvent.When the viscosity-average molecular weight is within the range, goodmolding processability is achieved, and the molded product has highimpact resistance, toughness, and chemical resistance.

The polycarbonate resin may be composed of two or more polycarbonateresins having different viscosity average molecular weights, as long asthe viscosity average molecular weight of the whole resin falls withinthe above range.

As described above, the polycarbonate resin may be used in the form ofan alloy in combination with a polyester resin, or a rubber-reinforcedresin and a polyester resin.

Examples of the polyester resin include: polymers obtained from (1) adicarboxylic acid having 2 to 20 carbon atoms and/or its esterderivative and (2) a diol component; polymers obtained from abifunctional oxycarboxylic acid compound; polymers obtained from acaprolactone compounds; and copolymers composed of (1), (2) and acompound selected from the group consisting of bifunctional oxycarboxylic acid compounds and lactone compounds. The copolymer ispreferably composed of (1), (2), and a bifunctional oxycarboxylic acidcompound. The number of carbon atoms refers to the total carbon atomsforming the carboxyl group and the chains and rings directly linked tothe carboxyl group.

The polyester resin is not particularly specified as long as it containsan ester bond in the main chain of the molecule, and may be a saturatedor unsaturated polyester resin. Among them, a saturated polyester resinis preferred. The polyester resin may be a homopolymer or a copolymerpolyester, and may be a crystalline or non-crystalline resin.

Examples of the polyester resin include homopolymer polyesters such aspolyalkylene terephthalate including polyethylene terephthalate (PET),polypropylene terephthalate (PPT), polybutylene terephthalate (PBT),polyhexamethylene terephthalate,polycyclohexane-1,4-dimethylterephthalate, and polyneopentylterephthalate, polyethylene isophthalates, and polyalkylene naphthalatessuch as polyethylene naphthalate, olybutylene naphthalate, andpolyhexamethylene naphthalate; copolymer polyesters composed mainly ofat least one of an alkylene terephthalate unit and an alkylenenaphthalate unit; and liquid crystalline polyesters. Among them,polybutylene terephthalate are preferred. They may be used alone or incombination of two or more thereof.

From the viewpoint of impact resistance, of the above polyester resins,polybutylene terephthalate usually has a solution viscosity of 0.5 to2.0 in terms of the limiting viscosity [η] (dl/g) measured at 25° C.using O-chlorophenol as the solvent. The limiting viscosity [η] (dl/g)of polyethylene terephthalate is usually from 0.5 to 2.0, and preferablyfrom 0.5 to 1.5, as measured at 25° C. in a mixed solvent containingequal parts of tetrachloromethane and phenol.

The number average molecular weight (Mn) of the aliphatic polyesterresin is usually from 10000 to 20000, preferably from 30000 to 200000,and the ratio of the weight average molecular weight (Mw) to the numberaverage molecular weight (Mn), or Mw/Mn is usually 3 or more, andpreferably 4 or more.

The polyamide resin is not particularly specified, as long as it has anacid amide bond (—CO—NH—) in the main chain. Specific examples includenylon 4, 6, 7, 8, 11, 12, 6.6, 6.9, 6.10, 6.11, 6.12, 6T, 6/6.6, 6/12,6/6T, and 6T/6I.

The end of the polyamide resin may be blocked by carboxylic acid oramine. Examples of the carboxylic acid include aliphatic monocarboxylicacids such as caproic acid, caprylic acid, capric acid, lauric acid,myristic acid, palmitic acid, stearic acid, and behenic acid. Examplesof the amine include aliphatic primary amines such as hexyl amine, octylamine, decyl amine, lauryl amine, myristyl amine, palmityl amine,stearyl amine, and behenyl amine.

The polyamide resin may be used alone or in combination of two or morethereof.

The degree of polymerization of the polyamide resin is not particularlyspecified. From the viewpoint of impact resistance, the relativeviscosity is usually from 1.6 to 6.0, and preferably from 2.0 to 5.0.The relative viscosity is measured at 30° C. in a solution prepared bydissolving 2 g of the polymer in 100 ml of formic acid (purity: 90% bymass).

Examples of the vinyl chloride resin include polyvinyl chloride resins,copolymers of vinyl chloride with other vinyl monomer copolymerizablewith vinyl chloride, acrylonitrile-butadiene copolymer blends, andchlorinated polyvinyl chloride resins prepared by chlorination ofpolyvinyl chloride.

Examples of the other vinyl monomer copolymerizable with vinyl chlorideinclude ethylene, propylene, maleate, vinyl acetate, (meth)acrylic acid,and (meth)acrylates. The average degree of polymerization of the vinylchloride resin is usually from 700 to 1800, and preferably from 1000 to1500.

In the process for producing a thermoplastic resin molded productaccording to the first aspect of the present invention, after theparticle heating step is carried out, the cooling step is preferablypreceded by a filling step of filling the thermoplastic resin in amolten state into the space left in the cavity.

In this case, after the particle heating step, the space left in thecavity after melting the thermoplastic resin particle composition isfilled with the thermoplastic resin in a molten state in the fillingstep. At that time, the portion in the cavity of the rubber die wherethe thermoplastic resin particle composition has been presented beforethe particle heating step, the lower part of the cavity of the rubberdie in a vertical direction, or the surface of the cavity of the rubberdie are filled with the thermoplastic resin obtained by melting thethermoplastic resin particle composition, thereby reducing the amount ofthe thermoplastic resin in a molten state to be newly filled.

As a result of this, the thermoplastic resin is filled into the whole ofthe cavity without increasing the filling pressure so high, whereby thedeformation and opening of the rubber die are effectively prevented.Therefore, resin leakage at the parting surface in the rubber die isprevented, and the thermoplastic resin molded product obtained throughthe cooling step has effectively improved properties such as appearance,shape and surface accuracy, and mechanical strength.

The thermoplastic resin particle composition and the thermoplastic resinin a molten state may have the same constitution.

In this case, when the thermoplastic resin molded product is moldedthrough the cooling step of cooling the thermoplastic resin filled intothe cavity, the resultant thermoplastic resin molded product has nointerface between the thermoplastic resin particle composition and thethermoplastic resin in a molten state.

The thermoplastic resin particle composition and the thermoplastic resinin a molten state may have intentionally different constitutions andcolors. In this case, the thermoplastic resin molded product haseffectively improved properties, and serves as a two color moldedproduct.

In the filling step, the thermoplastic resin in a molten state ispreferably filled into the cavity left in the space under an injectionpressure at 0.5 to 5 MPa.

In this case, when the thermoplastic resin is filled into the cavityunder an appropriate injection pressure within the predetermined range,the deformation and opening of the rubber die are effectively prevented,and the thermoplastic resin molded product has improved properties suchas shape and surface accuracy. In order to uniformly fill thethermoplastic resin into almost the whole of the cavity of the rubberdie, the injection pressure is preferably 0.5 MPa or more. In order toprevent deformation of the rubber die and resin leakage from the cavityof the rubber die, the injection pressure is preferably 5 MPa or less.

At any time, at least during the period before the placement step tobefore the particle heating step, a vacuum step of vacuuming the cavityor the space left in the cavity is preferably carried out.

In this case, the vacuum step further facilitates the filling of thethermoplastic resin in a molten state into the cavity, and facilitatesthe formation of a thermoplastic resin molded product with goodappearance and no bubble.

The vacuum step may be carried out at any time, at least during theplacement step, before or after the placement step, during the particleheating step, before or after the particle heating step, during thefilling step, or before or after the filling step.

The vacuum state refers to an absolute vacuum state, and a reducedpressure state with reference to the atmospheric pressure.

In the filling step, it is preferred that the thermoplastic resin in thecavity be heated by irradiation with electromagnetic waves havingwavelengths ranging from 0.78 to 2 μm through a rubber die.

In this case, in the filling step, when the thermoplastic resin in amolten state is filled into the cavity, the thermoplastic resin isheated selectively in preference to the rubber die, whereby theviscosity of the thermoplastic resin is kept low. As a result of this,the thermoplastic resin molded product has effectively improvedproperties such as shape and surface accuracy.

In the particle heating step and filling step, an electromagnetic wavegeneration means emitting electromagnetic waves having wavelengthsranging from 0.78 to 4 μm, and a filter decreasing the transmission ofelectromagnetic waves having wavelengths over 2 μm are used. Theelectromagnetic waves emitted from the electromagnetic wave generationmeans are transmitted through the filter, and the transmittedelectromagnetic waves after passing through the filter are irradiated tothe thermoplastic resin in the cavity through the rubber die, therebyheating the thermoplastic resin.

In this case, in the particle heating step and the filling step,electromagnetic waves having wavelengths ranging from 0.78 to 4 μm areemitted from the electromagnetic wave generation means, and thetransmitted electromagnetic waves after passing through the filter areirradiated to the thermoplastic resin through the rubber die. Theelectromagnetic waves emitted from the electromagnetic wave generationmeans include those having wavelengths over 2 μm, but the filterminimizes the irradiation of the rubber die with the electromagneticwaves having wavelengths over 2 μm. As a result of this, thethermoplastic resin filled into the cavity of the rubber die iseffectively irradiated with near-infrared rays (electromagnetic waves)having a wavelength of 2 μm or less. Therefore, the thermoplastic resinis effectively heated by the near-infrared rays having wavelengths of 2μm or less, without excessive heating of the rubber die.

The filter may be made of glass such as fused silica, or water chargedinto a container or passage. When the filter is made of water, the watermay be circulated or renewed, and the water heated by irradiation withelectromagnetic waves may be renewed as necessary, thereby effectivelycontrolling the temperature rise of the filter.

The thermoplastic resin composing the thermoplastic resin particlecomposition may be a non-crystalline resin.

The cooling rate of the thermoplastic resin in the rubber die made of arubber material is lower than those in a metal die. Therefore,crystallinity of the thermoplastic resin may increase during cooling,whereby the resin molded product may deteriorate in its dimensionalaccuracy and impact resistance. The use of a non-crystallinethermoplastic resin prevents the deterioration in the dimensionalaccuracy and impact resistance of the thermoplastic resin moldedproduct.

Examples of the non-crystalline resin include the above-describedrubber-reinforced styrene resins, styrene resins, acrylic resins,polycarbonate resins, and alloys of rubber-reinforced styrene resins andpolycarbonate resins. Among them, rubber-reinforced styrene resins arepreferred.

The bulk density of the thermoplastic resin particle composition ispreferably 0.4 g/cm³ or more.

In this case, the same effect as the third aspect of the presentinvention will be achieved.

The thermoplastic resin particle composition may contain 0.1 to 20% bymass of small thermoplastic resin particles having a particle size of 1to 100 μm, the balance being large thermoplastic resin particles largerthan the small thermoplastic resin particles.

In this case, the same effect as the fourth aspect of the presentinvention will be achieved.

In the placement step, it is preferred that the small thermoplasticresin particles be placed first in the cavity of the rubber die in anopened or closed state, and then the large thermoplastic resin particlesbe filled into the cavity of the rubber die.

In this case, in the placement step, the small thermoplastic resinparticles effectively adhere to the inner wall of the cavity, and thenthe large thermoplastic resin particles pass on the inner side of thesmall thermoplastic resin particles in the cavity. Therefore, thethermoplastic resin particles are smoothly filled into the cavity.

The small thermoplastic resin particles are easily placed by sprinklingthem over the surface of the cavity of the rubber die in an open state.

The bulk density of the large thermoplastic resin particles ispreferably 0.4 g/cm³ or more.

The maximum particle size of the large thermoplastic resin particles ispreferably 0.8 or less times the minimum width of the cavity.

As a result of this, difficulty in charging the large thermoplasticresin particles into the cavity is avoided.

The particle size of the large thermoplastic resin particles is morepreferably 0.7 or less times the minimum width of the cavity.

The large and small thermoplastic resin particles may be composed of theabove-described thermoplastic resin.

The thermoplastic resin particle composition may include thermoplasticresin particles and fine particles of at least one of an inorganicpowder and a lubricant, the number average particle size of thethermoplastic resin particles being from 200 to 3000 μm, the volumeaverage particle size of the fine particles being from 0.5 to 50 μm, andthe content of the fine particles being from 0.1 to 10 parts by masswith reference to 100 parts by mass of the thermoplastic resinparticles.

In this case, the same effect as the fifth aspect of the presentinvention will be achieved.

In the placement step, it is preferred that the fine particles be placedfirst in the cavity of the rubber die in an opened or closed state, andthen the thermoplastic resin particles be charged into the cavity of therubber die.

In this case, in the placement step, the fine particles effectivelyadhere to the inner wall surface of the cavity, and then thethermoplastic resin particles pass on the inner side of the fineparticles in the cavity. Therefore, the thermoplastic resin particlesare smoothly filled into the cavity.

The fine particles are easily placed by sprinkling them over the surfaceof the cavity of the rubber die in an opened state.

The number average particle size of the thermoplastic resin particles ispreferably 0.8 or less times the minimum width of the cavity.

As a result of this, difficulty in filling the thermoplastic resinparticles into the cavity is avoided.

The number average particle size of the thermoplastic resin particles ismore preferably 0.7 or less times the minimum width of the cavity.

Examples of the inorganic powder include talc, calcium carbonate,magnesium carbonate, mica, kaolin, calcium sulfate, barium sulfate,titanium white, white carbon, carbon black, aluminium hydroxide,magnesium hydroxide, glass fibers, glass fiber milled fibers, glassbeads, hollow glass, glass flakes, carbon fibers, milled carbon fibers,wollastonite, attapulgite, and whiskers such as silicon carbide whisker,zinc oxide whisker, aluminum borate whisker, potassium titanate whisker,and basic magnesium sulfate whisker. They may be used alone or incombination of two or more thereof. Among them, talc, zinc oxidewhisker, and basic magnesium sulfate whisker are preferred.

The inorganic powder is preferably talc.

Talc is a powder produced by pulverization of a mineral referred to astalc, and is composed of hydrous magnesium silicate (4SiO₂.3MgO.H₂O).Talc is composed mainly of about 60% by mass of SiO₂, about 30% by massof MgO. The talc in the present invention is in the form of fineparticles having a volume average particle size of 0.5 to 50 μm. Thesurface of the talc may be treated with a silane coupling agent or thelike.

The volume average particle size (50% average particle size) of the talcis more preferably from 1 to 30 μm, and even more preferably from 3 to15 μm.

The lubricant may be a known lubricant. Specific examples of thelubricant include compounds having a long-chain alkyl group and afunctional group, α-olefin (co)polymers such as ethylene or propylene,silicon-containing polymes such as dimethylpolysiloxane, copolymers ofα-olefin and a functional group-containing unsaturated compound,ethylene copolymers, propylene copolymers, ethylene-propylenecopolymers, polymers obtained by adding a functional group-containingunsaturated compound to a polymer such as a silicon-containing polymer,and polymers obtained by oxidizing polyethylene, polypropylene, or anethylene-propylene copolymer, and then adding a carboxyl group or thelike.

Examples of the functional group include a carboxyl group or its metalsalt, a hydroxyl group, an oxazoline group, an acid anhydride group, anester group, an amino group, an amide group, an epoxy group, anisocyanate group, an urethane group, and an urea group. Preferredfunctional groups include a carboxyl group or its divalent metal salt,an ester group, and an amide group. Examples of the salt of a carboxylgroup include metal salts such as sodium, potassium, lithium, calcium,magnesium, aluminum, zinc, barium, cadmium, manganese, cobalt, lead, andtin salts. The functional group-containing unsaturated compound may bethe above-described functional group-containing unsaturated compound.Preferred are compounds having a long-chain alkyl group and a functionalgroup, and ethylene copolymers.

The volume average particle size (50% average particle size) of thelubricant is more preferably from 1 to 30 μm, and even more preferablyfrom 3 to 15 μm.

The particle size of the thermoplastic resin particles is morepreferably from 200 to 2000 μm, and even more preferably from 350 to1500 μm. The bulk density of the thermoplastic resin particles ispreferably 0.4 g/cm³ or more.

The melt flow rate (220° C., 10 kg load) of the thermoplastic resin usedin the thermoplastic resin particles is preferably from 1 to 100 g/10min, more preferably from 5 to 80 g/10 min, and even more preferablyfrom 15 to 65 g/10 min.

The thermoplastic resin particle composition may include 0.0005 to 0.1parts by mass of an infrared ray absorbing agent with reference to 100parts by mass of the thermoplastic resin particles.

In this case, the same effect as the sixth aspect of the presentinvention will be achieved.

The infrared ray absorbing agent may be selected from various ones whichabsorb electromagnetic waves having near infrared ray wavelengthsranging from 0.78 to 2 μm.

The infrared ray absorbing agent may be inorganic or organic. Examplesof the inorganic infrared ray absorbing agent include metal oxides suchas tin oxide, zinc oxide, and copper oxide; antimony-doped tin oxide,indium-doped tin oxide, metal complex compounds of zinc oxide containingat least one element selected from the group consisting of In, Ga, Al,and Sb.

Examples of the organic infrared ray absorbing agent includeanthraquinone dyes, cyanine dyes, polymethine dyes, azomethine dyes, azodyes, polyazo dyes, diimonium dyes, aminium dyes, phthalocyanine dyes,naphthalocyanine dyes, indocyanine dyes, naphthoquinone dyes, indolephenol dyes, triallylmethane dyes, metal complex dyes, dithiol nickelcomplex dyes, azo cobalt complex dyes, and squarylium dyes.

The thermoplastic resin composition may include 0.05 to 30 parts by massof a coloring agent with reference to 100 parts by mass of thethermoplastic resin.

In this case, the thermoplastic resin molded product to be molded willhave a whiteness value of 30% or more and an appropriate color.

The content of the coloring agent is more preferably from 0.1 to 15parts by mass, and even more preferably from 0.1 to 10 parts by masswith reference to 100 parts by mass of the thermoplastic resin.

The coloring agent may be a dye, an inorganic pigment, or an organicpigment. They may be used in combination. The color of the coloringagent is not particularly specified, and may have a white, red, yellow,blue, or green color.

Examples of the dye include nitroso dyes, nitro dyes, azo dyes, stilbeneazo dyes, ketoimine dyes, triphenylmethane dyes, xanthene dyes, acridinedyes, quinoline dyes, methine/polymethine dyes, thiazole dyes,indamine/indophenol dyes, azine dyes, oxazine dyes, thiazine dyes,sulfur dyes, aminoketone/oxyketone dyes, anthraquinone dyes, indigoiddyes, and phthalocyanine dyes.

Examples of the inorganic pigment include white inorganic pigments, redinorganic pigments, yellow inorganic pigments, green inorganic pigments,and blue inorganic pigments. They may be used alone or in combination oftwo or more thereof.

Examples of the white inorganic pigment include TiO₂, Al₂O₃.nH₂O,[ZnS+BaSO₄], CaSO₄.2H₂O, BaSO₄, CaCO₃, and 2PbCO₃.Pb(OH)₂.

Examples of the red inorganic pigment include CdS.nCdSe,PbCrO₄.mPbMoO₄.nPbSO₄, TiO₂.Sb₂O₃.NiO, Zn—Fe complex oxides (forexample, ZnO.Fe₂O₃), and Zn—Fe—Cr complex oxides (for example,ZnO.Fe₂O₃.Cr₂O₃).

Examples of the yellow inorganic pigment include TiO₂.BaO.NiO,TiO₂.NiO.Sb₂O₃, Fe₂O₃.H₂O, PbCrO₄, Pb(SbO₃)₂, Pb₂(SbO₂)₂, Ti—Sb—Nicomplex oxides, and Ti—Sb—Cr complex oxides.

Examples of the green inorganic pigment include Cu(C₂H₃O₂)₃, Cu(AsO₂)₂,CoO.nZnO, BaMnO₂, Cu₂(OH)₂(CO₃), and Ti—Co—Ni—Zn complex oxides.

Examples of the blue inorganic pigment include CoO.nAl₂O₃,CoO.nSnO.mMgO, and Na₆Al₆(SiO₄)₆.2Na₃SO₄.

Examples of the organic pigment include azo pigments such as azo lakepigments, benzoimidazolone pigments, diarylide pigments, and condensedazo pigments; phthalocyanine pigments such as phthalocyanine blue andphthalocyanine green; and condensed polycyclic pigments such asisoindolinone pigments, quinophthalone pigments, quinacridone pigments,perylene pigments, anthraquinone pigments, perinone pigments, anddioxazine violet.

When the chromatic coloring agent is a deep coloring agent by itself,its color may be lightened with a white coloring agent, therebyachieving an intended whiteness.

When a transparent thermoplastic resin molded product having a hazevalue of 20% or less is molded from a thermoplastic resin containing aninfrared ray absorbing agent, the thermoplastic resin used herein may beselected from various transparent (or translucent) thermoplastic resins,as long as the molded product having a thickness of 2.5 mm made from thethermoplastic resin has a haze value of 20% or less as measuredaccording to JIS K7136. Specific examples include: the styrene resinssuch as AS resins and MS resins; the rubber-reinforced styrene resinssuch as transparent ABS resins and acrylic resins; the polycarbonateresins and polyester resins such as PET resins, PEN resins, vinylchloride resins, cycloolefin resins, polymethylpentene resins, andpolyarylate resins. Among them, transparent ABS resins, acrylic resins,and polycarbonate resins are preferred for achieving good moldabilityand impact resistance.

The transparent ABS is preferably a rubber-reinforced vinyl resinobtained by polymerizing monomer components containing 50% by mass ormore of a (meth)acrylate ester compound in the presence of a rubberypolymer, or a mixture of the rubber-reinforced vinyl resin and a(co)polymer containing structural units derived from a vinyl monomer.

The (meth)acrylate ester compound used in the transparent ABS resin maybe the above-described (meth)acrylate ester compound. Among theexamples, methyl acrylates, butyl acrylates, and methyl methacrylatesare preferred.

The rubbery polymer used in the transparent ABS resin may be theabove-described rubbery polymer (a1). Among the examples, conjugateddiene rubbers, olefin rubbers, and acrylic rubbers are preferred. Theymay be used alone or in combination of two or more thereof.

The graft rate of the transparent ABS resin is preferably from 10 to100%, more preferably from 15 to 90%, and even more preferably from 20to 70%. If the graft rate is less than 10%, the transparentthermoplastic resin molded product to be obtained may have insufficientappearance or impact strength. On the other hand, if the graft rate ismore than 100%, the molding processability may deteriorate.

The limiting viscosity [η] (measured in methyl ethyl ketone at 30° C.)of the methyl ethyl ketone-soluble component, which is the matrixcomponent, of the transparent ABS resin is preferably from 0.1 to 1.0dl/g, more preferably from 0.2 to 0.9 dl/g, and even more preferablyfrom 0.3 to 0.7 dl/g. When the limiting viscosity [η] is within theabove range, a transparent thermoplastic resin molded product havinggood impact resistance and molding processability (flowability) will beobtained. The graft rate (%) and limiting viscosity [η] are readilycontrolled by changing the type and amount of the polymerizationinitiator, chain transferring agent, emulsifier, and solvent, and thetime and temperature of polymerization.

The difference of the refractive index between the rubbery polymer(rubber component) of the transparent ABS resin and the matrix resin ispreferably 0.05 or less, more preferably 0.02 or less, and even morepreferably 0.01 or less. When the difference of the refractive index iswithin the range, a thermoplastic resin molded product having goodtransparency will be obtained.

When a transparent thermoplastic resin molded product having a whitenessvalue of 30% or more is molded from a thermoplastic resin containing aninfrared ray absorbing agent, the thermoplastic resin may be selectedfrom the above-described thermoplastic resins. Preferred examplesinclude rubber-reinforced styrene resins, olefin resins, acrylic resins,polyester resins, polyamide resins, alloys of polyester resins andpolycarbonate resins, alloys of rubber-reinforced styrene resins andpolycarbonate resins, and alloys of rubber-reinforced styrene resins andpolyester resins.

The thermoplastic resin particle composition may contain any additiveaccording to the intended use. Examples of the additive include fillers,heat stabilizers, antioxidants, ultraviolet light inhibitors,preservatives, antistatic agents, plasticizing agents, lubricants, flameretardants, antibacterial agents, coloring agents, fluorescentbrightening agents, luminous pigments, fluorescent dyes, light diffusingagents, crystal nucleating agents, flow improvers, impact modifiers,infrared ray absorbing agents, photochromic agents, photocatalyticantifouling agents, and polymerization initiators.

Examples of the filler include talc, clay, wollastonite, calciumcarbonate, glass fiber, glass beads, glass balloon, milled fiber, glassflakes, carbon fibers, carbon flakes, carbon beads, carbon milledfibers, metal flakes, metal fibers, metal-coated glass fibers,metal-coated carbon fibers, metal-coated glass flakes, silica, ceramicparticles, ceramic fibers, aramid particles, aramid fibers, polyarylatefibers, graphite, conductive carbon black, and various whiskers. Theymay be used alone or in combination of two or more thereof.

The content of the filler is usually from 0.1 to 5 parts by mass withreference to 100 parts by mass of the thermoplastic resin particlecomposition.

Examples of the heat stabilizer include phosphites, hindered phenols,and thioethers. They may be used alone or in combination of two or morethereof.

The content of the heat stabilizer is usually from 0.01 to 2 parts bymass with reference to 100 parts by mass of the thermoplastic resinparticle composition.

Examples of the antioxidant include hindered amines, hydroquinones,hindered phenols, and sulfur-containing compounds. They may be usedalone or in combination of two or more thereof.

The content of the antioxidant is usually from 0.01 to 2 parts by masswith reference to 100 parts by mass of the thermoplastic resin particlecomposition.

Examples of the ultraviolet absorber include benzophenones,benzotriazoles, salicylates, and metal complex salts. They may be usedalone or in combination of two or more thereof. The ultraviolet absorbermay be preferably combined with hindered amines.

The content of the ultraviolet absorber is usually from 0.05 to 2 partsby mass with reference to 100 parts by mass of the thermoplastic resinparticle composition.

The content of the preservatives is usually from 0.01 to 2 parts by masswith reference to 100 parts by mass of the thermoplastic resin particlecomposition.

The content of the antistatic agent is usually from 0.1 to 5 parts bymass with reference to 100 parts by mass of the thermoplastic resinparticle composition.

The content of the plasticizing agent is usually from 0.5 to 5 parts bymass with reference to 100 parts by mass of the thermoplastic resinparticle composition.

Examples of the lubricant include fatty acid esters, hydrocarbon resins,paraffin, higher fatty acids, oxy-fatty acids, fatty acid amides,alkylene bis-fatty acid amides, aliphatic ketones, fatty acid loweralcohol esters, fatty acid polyhydric alcohol esters, fatty acidpolyglycol esters, aliphatic alcohols, polyhydric alcohols, polyglycols,polyglycerols, metallic soap, silicon, and modified silicon. They may beused alone or in combination of two or more thereof.

The content of the lubricant is usually from 0.5 to 5 parts by mass withreference to 100 parts by mass of the thermoplastic resin particlecomposition.

Examples of the flame retardant include organic flame retardants,inorganic flame retardants, and reactive flame retardants. They may beused alone or in combination of two or more thereof.

The content of the flame retardant is usually from 0.5 to 30 parts bymass with reference to 100 parts by mass of the thermoplastic resinparticle composition.

When the thermoplastic resin particle composition of the presentinvention contains a flame retardant, the flame retardant is preferablycombined with a flame retardant aid. Examples of the flame retardant aidinclude antimony compounds such as diantimony trioxide, diantimonytetraoxide, diantimony pentaoxide, sodium antimonate, and antimoniumtartaricum, zinc borate, barium metaborate, hydrated alumina, zirconiumoxide, ammonium polyphosphate, tin oxide, and iron oxide. They may beused alone or in combination of two or more thereof.

The content of the antibacterial agent is usually from 0.1 to 5 parts bymass with reference to 100 parts by mass of the thermoplastic resinparticle composition.

The coloring agent may be an inorganic pigment, an organic pigment, or adye. They may be used in combination.

Examples of the inorganic pigment include oxides such as zinc white,titanium dioxide, red oxide, chromium oxide, and iron black; sulfidessuch as cadmium yellow, cadmium orange, and cadmium red; chromates suchas chrome yellow, zinc yellow, and chromium vermilion; ferrocyanidessuch as Berlin blue; silicate salts such as ultramarine blue; andinorganic coloring agents such as carbon black and metal powder.

Examples of the organic pigment include phthalocyanine pigments,condensed azo pigments, azo lake pigments, quinacridone pigments,dioxazine pigments, isoindolinone pigments, and condensed polycyclicpigments.

Examples of the dye include anthraquinone dyes, perylene dyes, perinonedyes, quinoline dyes, nitro dyes, nitroso dyes, azo dyes, triphenyldyes, thiazole dyes, methine dyes, oxazine dyes, indophenol dyes, ketonedyes, thiazine dyes, and indigo dyes.

The content of the coloring agent is usually 10 parts by mass or less,preferably from 0.0005 to 5 parts by mass, and more preferably from0.001 to 2 parts by mass with reference to 100 parts by mass of thethermoplastic resin particle composition.

Examples of the light diffusing agent include crosslinked acrylparticles, crosslinked silicon particles, very thin glass flakes, andcalcium carbonate particles.

Examples of the photocatalytic antifouling agent include fine particlesof titanium oxide and zinc oxide.

Examples of the impact modifier include graft rubber.

EXAMPLES

Examples of the process of the present invention for producing athermoplastic resin molded product and the thermoplastic resin particlecomposition of the present invention are described below with referenceto drawings.

Example 1

The process for producing the thermoplastic resin molded product 60 ofthe present example includes: as shown in FIG. 1, a placement step ofcharging a thermoplastic resin (thermoplastic resin particlecomposition) 6A in a particulate state into a cavity 22 of a rubber die2 made of a rubber material; as shown in FIG. 2, a particle heating stepof irradiating the thermoplastic resin 6A in a particulate state in thecavity 22 with electromagnetic waves having wavelengths ranging from0.78 to 2 μm through the rubber die 2, thereby heating to melt thethermoplastic resin 6 in a particulate (powdery) state; as shown inFIGS. 2 and 3, a filling step of filling a thermoplastic resin 6B in amolten state into a space 220 left in the cavity 22; and a cooling stepof cooling a thermoplastic resin 6 in the cavity 22 thereby obtaining athermoplastic resin molded product 60.

The process for producing the thermoplastic resin molded product 60 ofthe present example is described below in detail with reference to FIGS.1 to 6.

In the present example, the thermoplastic resin 6 is an ABS resin whichis a non-crystalline resin and a rubber-reinforced styrene resin.

The rubber die 2 of the present example is made of transparent ortranslucent silicone rubber. The rubber die 2 may be made by placing amaster model (for example, a handmade actual object) of thethermoplastic resin molded product 60 to be molded in a liquid siliconerubber, curing the silicone rubber, cutting to open the cured siliconerubber, and taking out the master model from the silicone rubber.

As shown in FIG. 1, the rubber die 2 of the present example is composedof two split dies 21 divided by one parting surface 20. Alternatively,when the shape of the thermoplastic resin molded product 60 to be moldedis complicated, the rubber die 2 may be composed of three or more splitdies 21. During molding, a plurality of the split dies 21 maintain thecombined state by any means for preventing mold opening. The partingsurface 20 may be formed into an irregular wave shape, therebyfacilitating the alignment of the split dies 21.

In the process of the present example for producing the thermoplasticresin molded product 60, injection molding of the thermoplastic resin 6into the rubber die 2 is carried out using a molding machine 1. As shownin FIGS. 1 to 3, a molding machine 1 includes a pressure vessel 3, avacuum pump 31, an injection cylinder 52, an ejection cylinder 53, anelectromagnetic wave generation means 4, and a filter 43.

The pressure vessel 3 accommodates the rubber die 2, and creates avacuum state by the vacuum pump 31 connected to the pressure vessel 3.The injection cylinder 52 injects the thermoplastic resin 6A in aparticulate state into the cavity 22 through an inlet 23 formed in therubber die 2. The ejection cylinder 53 ejects the thermoplastic resin 6Bin a molten state under a specified pressure into the cavity 22 throughthe inlet 23 formed in the rubber die. In the present example, thepressure of the thermoplastic resin 6B in a molten state ejected fromthe ejection cylinder 53 into the rubber die 2 is from 0.5 to 5 MPa.

The electromagnetic wave generation means 4 includes an electromagneticwave (light) generation source 41 and a reflector 42 for guiding theelectromagnetic waves generated by the generation source 41 toward therubber die 2. The electromagnetic wave generation means 4 of the presentexample includes a near-infrared halogen heater having a light intensitypeak in the vicinity of about 1.2 μm in the near-infrared region. Thenear-infrared halogen heater emits electromagnetic waves havingwavelengths ranging from 0.78 to 4 μm. The filter 43 of the presentexample is made of fused silica which decreases the transmission of theelectromagnetic waves having wavelengths over 2 μm.

In FIGS. 2 and 3, the electromagnetic waves emitted from theelectromagnetic wave generation means 4 are indicated with an arrow X.

The ABS resin used as the thermoplastic resin 6 has a higher absorbanceof the electromagnetic waves (light) having wavelengths ranging from0.78 to 2 μm (a scale representing the absorption intensity of lighthaving a specific wavelength) than silicone rubber used as the rubberdie 2 made of rubber. The absorbance may be measured using, for example,UV3100 manufactured by Shimadzu Co., Ltd.

FIG. 4 shows graphs of the optical transmittance in the transparent andtranslucent silicone rubbers, taking the wavelength (nm) as abscissa,and the optical transmittance (%) as ordinate. The graph indicates thatthe silicone rubbers transmit light having wavelengths ranging from 200to 2200 (nm). Therefore, when near-infrared rays (light havingwavelengths ranging from 0.78 to 2 μm) in the wavelength range isirradiated to the surface of the rubber die 2 made of silicone rubber,much of the near-infrared rays transmits through the rubber die 2 and isabsorbed by the thermoplastic resin 6. Furthermore, the thermoplasticresin 6 is heated selectively in preference to the rubber die 2.

The process for producing the thermoplastic resin molded product 60using the molding machine 1 is described below.

In the production process of the present example, the thermoplasticresin 6A in a particulate state and the thermoplastic resin 6B in amolten state are used for molding the thermoplastic resin molded product60 by filling the thermoplastic resin 6 into the rubber die 2. In thepresent example, the thermoplastic resin 6A in a particulate state andthe thermoplastic resin 6B in a molten state are made of an ABS resinhaving the same constitution.

When the thermoplastic resin molded product 60 is molded, firstly, asthe placement step shown in FIG. 1, the injection cylinder 52 is set inthe inlet 23 of the mold, and the thermoplastic resin 6A in aparticulate state is filled into almost the whole of the cavity 22 ofthe rubber die 2. The thermoplastic resin 6A in a particulate state maybe filled under its self weight, or using vibration or air stream.Subsequently, as the vacuum step shown in FIG. 2, the vacuum pump 31vacuums the pressure vessel 3, thereby vacuuming the space 220 left inthe cavity 22 of the rubber die 2.

Subsequently, as the particle heating step shown in FIG. 2, theelectromagnetic waves having wavelengths ranging from 0.78 to 4 μmemitted from the electromagnetic wave generation means 4 is transmittedthrough the filter 43, and the transmitted electromagnetic passedthrough the filter 43 is irradiated to the thermoplastic resin 6 in thecavity 22 through the rubber die 2. At that time, the thermoplasticresin 6A in a particulate state is selectively heated (the thermoplasticresin 6 is more heated) in preference to the rubber die 2, based on thedifference of the physical properties of the rubber material composingthe rubber die 2 and the thermoplastic resin 6 in a powdery state. As aresult of this, the thermoplastic resin 6A in a particulate state ismelted with the temperature rise of the rubber die 2 suppressed. Inaddition, as a result of the melting of the thermoplastic resin 6A in aparticulate state, the space 220 to be filled with the thermoplasticresin 6 is newly formed in the cavity 22.

Subsequently, as the filling step shown in FIG. 3, the ejection cylinder53 is set in the inlet 23 of the mold, and the thermoplastic resin 6B ina molten state is filled into the space 220 left in the cavity 22 underan injection pressure of 0.5 to 5 MPa. In the filling step of thepresent example, irradiation of the thermoplastic resin 6 with thetransmitted electromagnetic waves through the rubber die 2 is continued,thereby heating the thermoplastic resin 6 in the cavity 22.

When the thermoplastic resin 6B in a molten state is filled, the lowerpart of the cavity 22 of the rubber die 2 in a vertical direction isfilled with the thermoplastic resin 6 produced by melting thethermoplastic resin 6A in a particulate state, thereby reducing theamount of the thermoplastic resin 6B in a molten state to be newlyfilled.

As a result of this, the thermoplastic resin 6 is filled into the wholeof the cavity 22 without increasing the filling pressure (injectionpressure) so high, whereby the deformation and opening of the rubber die2 are effectively prevented. Therefore, resin leakage at the partingsurface 20 in the rubber die 2 is prevented, and the thermoplastic resinmolded product 60 obtained through the cooling step has effectivelyimproved properties such as shape and surface accuracy.

In addition, the thermoplastic resin 6A in a particulate state and thethermoplastic resin 6B in a molten state are made of the thermoplasticresin 6 having the same constitution, whereby the formation of aninterface between different resins is prevented in the thermoplasticresin molded product 60.

Therefore, according to the process of the present example for producingthe thermoplastic resin molded product 60, when the thermoplastic resin6 is molded using the rubber die 2, the thermoplastic resin moldedproduct 60 has effectively improved properties such as shape and surfaceaccuracy. The present example is markedly effective when thethermoplastic resin molded product 60 to be molded is large orthin-walled, or when the thermoplastic resin 6 used for molding has ahigh viscosity.

(Confirmatory Test 1)

In the present confirmatory test, the thermoplastic resin 6A in aparticulate state having different particle sizes (hereinafter referredto as particles) were used. On the basis of the difference of theparticle size, the difference of the temperature rise rate when heatedby the electromagnetic wave generation means 4 (near-infrared halogenheater) was measured. The particles used in the present confirmatorytest were classified by sieves of different sizes. The sample A wasretained on a sieve having an aperture of 710 μm, the sample B wasretained on a sieve having an aperture of 250 μm after passing through asieve having an aperture of 710 μm, the sample C passed through a sievehaving an aperture of 250 μm, and the sample D had a volume averageparticle size of 55 μm. The sample E was a 1:1 mixture of the samples Aand C, and the sample F was a 1:1 mixture of the samples A and D.

In order to measure the temperature rise rate, an O ring was placed on asilicone rubber stage, the particles were filled into the O ring, andfused silica as a filter was placed on the O ring. The particles wereirradiated through the filter with electromagnetic waves havingwavelengths ranging from 0.78 to 2 μm emitted from a near-infraredhalogen heater (voltage: 80 V), and the particle temperature wasmeasured by a thermocouple. The electromagnetic waves were irradiateduntil the temperatures of the samples A to F reached 250° C., thedistance between the near-infrared halogen heater and the filter was 200mm, the thickness of the fused silica was 5 mm, and the inside diameterof the O ring was 30.4 mm.

TABLE 1 Bulk Angle of Tempeature Density Repose Rise Rate Mass SamplesParticle Size (μm) (g/cm³) (°) (° C./sec) (g) A 710 μmON 0.596 40.2 2.261.63 B 710 μmPass~250 0.541 38.6 2.88 1.51 μmON C 250 μmPass 0.384 43.05.29 1.15 D Volume Average 0.326 50.4 3.90 0.95 Particle Size 55 μm EA:C = 1:1 0.481 42.3 2.40 1.43 F A:D = 1:1 0.452 46.6 2.82 1.29

Table 1 lists the measurements of the bulk density (g/cm³), angle ofrepose (°), temperature rise rate (° C./sec), and mass (g) of thesamples A to F. FIG. 5 shows graphs of the bulk density and angle ofrepose of the samples A to F, and FIG. 6 shows the relationship betweenthe bulk density and the temperature rise rate of the samples A to F. InFIG. 5, the bar graph shows the bulk density G, and the line graph showsthe angle of repose H.

FIG. 5 indicates that the smaller the sample particle size is, thesmaller the bulk density is. On the other hand, the smaller the sampleparticle size is, the larger the angle of repose is, though notnecessarily correct.

FIG. 6 indicates that the smaller the sample particle size (bulkdensity) is, the higher the temperature rise rate is. The temperaturerise rates of the samples C and D having a small particle size were sohigh that there was a large difference in the particle temperaturebetween the side irradiated with the electromagnetic waves and the otherside, which resulted in the development of burning defects in theparticles. The result suggests that the bulk density of the particles(thermoplastic resin 6A in a particulate state) is preferably 0.4 g/cm³or more.

On the other hand, when the bulk density increases with the increase ofthe particle size, the temperature rise rate decreases, which results inthe necessity of increasing the time of electromagnetic wave irradiationfor heating the particles. As a result of this, the rubber die 2 maydevelop a defect such as burning. On that account, the bulk density ofthe particles (thermoplastic resin 6A in a particulate state) may be 0.8g/cm³ or less, and is more preferably 0.7 g/cm³ or less.

The temperature rise rates of the samples A and B were favorable,suggesting that the particle size of the particles is preferably morethan 250 μm. The temperature rise rates of the samples E and F were alsofavorable, suggesting that the particles having particle sizes of morethan 250 μm and 250 μm or less may be mixed.

The average particle size of the particles may be, for example, from 300to 2000 μm, and is more preferably from 350 to 1500 μm. The angle ofrepose of the particles may be 48° or less, and is more preferably 46°or less.

Example 2

The thermoplastic resin particle composition 6A of the present exampleis to be filled into the cavity 22 of the rubber die 2 made of a rubbermaterial, and heated to be melted by irradiation with electromagneticwaves having wavelengths ranging from 0.78 to 2 μm through the rubberdie 2. The thermoplastic resin particle composition 6A contains 0.1 to20% by mass of the small thermoplastic resin particles 62 having aparticle size of 1 to 100 μm, the balance being the large thermoplasticresin particles 61 having a particle size of 200 to 3000 μm.

The thermoplastic resin 6 (the large thermoplastic resin particles 61,small thermoplastic resin particles 62, and thermoplastic resinparticles 6B in a molten state) used in the present example is an ABSresin which is a non-crystalline rubber-reinforced styrene resin.

Subsequently, the process for producing the thermoplastic resin moldedproduct 60 using the molding machine 1 is described in detail withreference to FIGS. 1 to 3.

In the process of the present example for producing the thermoplasticresin molded product 60, the thermoplastic resin particle composition 6Aand the thermoplastic resin 6B in a molten state are used for moldingthe thermoplastic resin molded product 60 by filling the thermoplasticresin 6 into the rubber die 2. In the present example, the thermoplasticresin particle composition 6A and the thermoplastic resin 6B in a moltenstate are ABS resins having the same constitution.

When the thermoplastic resin molded product 60 is molded, firstly, asthe placement step shown in FIG. 1, the small thermoplastic resinparticles 62 having a particle size of 1 to 100 μm are sprinkled overthe surface of the cavity 22 at the split die 21 of the rubber die 2 inan opened state. Subsequently, the injection cylinder 52 is set in theinlet 23 of the rubber die 2 in a closed state, and the largethermoplastic resin particles 61 having a particle size of 200 to 3000μm are charged into the cavity 22 of the rubber die 2. At that time, thethermoplastic resin particle composition 6A charged into the cavity 22is composed of 80 to 99.9% by mass of the large thermoplastic resinparticles 61, and 0.1 to 20% by mass of the small thermoplastic resinparticles 62. The thermoplastic resin particle composition 6A is placedin (filled into) almost the whole of the cavity 22.

When the small thermoplastic resin particles 62 are sprinkled over thesurface of the cavity 22, most part of the small thermoplastic resinparticles 62 adheres to the inner wall surface 221 of the cavity 22. Thesmall thermoplastic resin particles 62 effectively adhere to the innerwall surface 221 of the cavity 22 made of silicone rubber, because therubber die 2 of the present example is made of silicone rubber, and thesmall thermoplastic resin particles 62 have a particle size of 1 to 100μm.

When the large thermoplastic resin particles 61 are charged into thecavity 22, the small thermoplastic resin particles 62 adhere to theinner wall surface 221 of the cavity 22. As a result of this, the largethermoplastic resin particles 61 pass (fall) on the inner side of thesmall thermoplastic resin particles 62 in the cavity 22. Therefore, thethermoplastic resin particles 61 and 62 are smoothly filled into thecavity 22. The large and small thermoplastic resin particles 61 and 62may be filled under their self weights, or using vibration or airstream.

Subsequently, as the vacuum step shown in FIG. 2, the vacuum pump 31vacuums the pressure vessel 3, thereby vacuuming the space 220 left inthe cavity 22 of the rubber die 2.

Subsequently, as the particle heating step shown in FIG. 2, theelectromagnetic waves having wavelengths ranging from 0.78 to 4 μmemitted from the electromagnetic wave generation means 4 are transmittedthrough the filter 43, and the transmitted electromagnetic waves afterpassing through the filter 43 are irradiated to the thermoplastic resinparticle composition 6A in the cavity 22 through the rubber die 2. Atthat time, the thermoplastic resin particle composition 6A isselectively heated (the thermoplastic resin particle composition 6A ismore strongly heated) in preference to the rubber die 2, based on thedifference of the physical properties of the rubber material composingthe rubber die 2 and the thermoplastic resin particle composition 6A. Asa result of this, the thermoplastic resin particle composition 6A ismelted with the temperature rise of the rubber die 2 suppressed. Inaddition, as a result of the melting of the thermoplastic resin particlecomposition 6A, the space 220 to be filled with the thermoplastic resin6 is newly formed in the cavity 22.

The state of the cavity 22 after the particle heating step variesaccording to the molding conditions. For example, when the thermoplasticresin 6 has poor flowability, the thermoplastic resin 6 in a moltenstate will not readily fall into the lower part of the cavity 22, andmany bubbles likely accumulate in the middle of the cavity 22. When thethermoplastic resin 6 has good flowability, the thermoplastic resin 6 ina molten state likely fall into the lower part of the cavity 22. Whenthe vacuum step is carried out as in the present example, the rubber die2 will be deformed to collapse the gap (space 220) in the cavity 22, andthe thermoplastic resin 6 is likely present on the surface of the cavity22.

Subsequently, as the filling step shown in FIG. 3, the ejection cylinder53 is set in the inlet 23 of the mold, and the thermoplastic resin 6B ina molten state is filled into the space 220 left in the cavity 22 underan injection pressure of 0.1 to 5 MPa. In the filling step of thepresent example, irradiation of the thermoplastic resin 6 with thetransmitted electromagnetic waves through the rubber die 2 is continued,thereby heating the thermoplastic resin 6 in the cavity 22.

When the thermoplastic resin 6B in a molten state is filled, the surfaceof the cavity 22 of the rubber die 2 (rubber surface) is filled with thethermoplastic resin 6 produced by melting the thermoplastic resinparticle composition 6A, thereby reducing the amount of thethermoplastic resin 6B in a molten state to be newly filled.

As a result of this, the thermoplastic resin 6 is filled into the wholeof the cavity 22 without increasing the filling pressure (injectionpressure) so high, whereby the deformation and opening of the rubber die2 are effectively prevented. Therefore, resin leakage at the partingsurface 20 in the rubber die 2 is prevented, and the thermoplastic resinmolded product 60 obtained through the cooling step has effectivelyimproved properties such as appearance, shape and surface accuracy, andmechanical strength.

The thermoplastic resin particle composition 6A and the thermoplasticresin 6B in a molten state are made of the thermoplastic resin 6 havingthe same constitution, thereby preventing the formation of an interfacebetween resins in the resultant thermoplastic resin molded product 60.

Therefore, according to the process of the present example for producingthe thermoplastic resin molded product 60, when the thermoplastic resin6 is molded using the rubber die 2, the thermoplastic resin moldedproduct 60 has effectively improved properties such as appearance,shape, and surface accuracy, and mechanical strength. The presentexample is markedly effective when the thermoplastic resin moldedproduct 60 to be molded is large or thin-walled, or when thethermoplastic resin 6 used for molding has a high viscosity.

(Effect Simulation)

FIGS. 7 and 8 are enlarged views of the states of filling thethermoplastic resin particles 61 and 62 into the cavity 22 of the rubberdie 2. FIG. 7 shows a state of filling the large and small thermoplasticresin particles 61 and 62 into the cavity 22, and FIG. 8 shows a stateof filling the large thermoplastic resin particles 61 alone into thecavity 22.

As shown in FIG. 8, when the large thermoplastic resin particles 61 arefilled alone into the cavity 22, the large thermoplastic resin particles61 adhere to the inner wall surface 221 of the cavity 22. In this case,it is likely difficult that another large thermoplastic resin particles61 pass (fall) on (indicated by an arrow T) the inner side of the largethermoplastic resin particles 61.

On the other hand, as shown in FIG. 7, when the large thermoplasticresin particles 61 are filled into the cavity 22 after filling the smallthermoplastic resin particles 62, the small thermoplastic resinparticles 62 effectively adhere to the inner wall surface 221 of thecavity 22, and the large thermoplastic resin particles 61 likely pass(fall) on (indicated by an arrow T) the inner side of the smallthermoplastic resin particles 62 with little adhesion to the inner wallsurface 221 of the cavity 22. As a result of this, almost the whole ofcavity 22 is likely effectively filled with the thermoplastic resinparticle composition 6A.

(Confirmatory Test 2)

The present confirmatory test examined improvements in properties(surface appearance) and mechanical strength (impact resistance)achieved by the use of the thermoplastic resin particle composition 6Ain Example 2 for the molding of a thermoplastic molded product.

In the present confirmatory test, five types of thermoplastic resinparticles (particles A, B, C, D, and E) were prepared.

(Particle A) 100 parts by mass of an ABS resin (“TECHNO ABS 330”manufactured by Techno Polymer Co., Ltd., MFR 42 (g/10 min)) and 0.5parts by mass of carbon black were extruded using a single screwextruder (40 mm diameter, cylinder temperature 220° C.) to obtain blackthermoplastic resin particles. The black thermoplastic resin particleswere formed into particles A having a number average particle size of700 μm using an extruder equipped with a strand cutter (formicropellets) manufactured by Gala Industries, Inc. The particles A hada bulk density of 0.63 g/cm³ as measured according to JIS K7365.

(Particles B) The black thermoplastic resin particles werefreeze-crushed using a freeze crusher (manufactured by Imoto MachineryCo., Ltd.) to obtain the particles B having a number average particlesize of 55 μm. The particles B had a bulk density of 0.33 g/cm³ asmeasured according to JIS K7365. The particles B had a particle size of1 to 100 μm.

(Particles C) The black thermoplastic resin particles were used as theywere to obtain the particles C having a number average particle size of3500 μm. The particles C had a bulk density of 0.65 g/cm³ as measuredaccording to JIS K7365.

(Particles D) The black thermoplastic resin particles werefreeze-crushed using a freeze crusher (manufactured by Imoto MachineryCo., Ltd.), and then sieved to obtain the particles D having a numberaverage particle size of 1300 μm. The particles D had a bulk density of0.59 g/cm³ as measured according to JIS K7365.

(Particles E) The black thermoplastic resin particles werefreeze-crushed using a freeze crusher (manufactured by Imoto MachineryCo., Ltd.), and then sieved to obtain the particles E having a numberaverage particle size of 460 μm. The particles E had a bulk density of0.51 g/cm³ as measured according to JIS K7365.

The particles A, C, D, and E are free from thermoplastic resin particleshaving a particle size of 100 μm or less.

The number average particle size was measured through the image analysisof micrographs using an image analysis software (“Image Pro Plus”,manufactured by Media Cybernetics Inc.). 100 or more samples weresubjected to image processing.

In the present confirmatory test, a rectangular cavity 22 having a sizeof 125 mm×12.5 mm×3.2 mm was made from silicone rubber. The minimumwidth dimension of the cavity 22 was 3.2 mm. Using the molding machine 1described in Example 1, the particles A, B, C, D, and E wererespectively filled into the cavity 22, and then heated to be melted. Athermoplastic resin in a molten state was additionally filled, and thencooled to obtain samples of a thermoplastic resin molded product.

Table 2 lists the results of the observation of surface appearance andthe measurements of the impact resistance of the inventions 1 to 5molded from the thermoplastic resin particle composition 6A composed ofany of the particles A, B, C, D, and E, and the comparisons 1 to 3molded from the thermoplastic resin particles composed of the particlesA, B, or C.

TABLE 2 Inventions Comparisons 1 2 3 4 5 1 2 3 Particles A 99.5 99 95100 75 99 (Number Average Particle Size 700 μm) (% by mass) Particles B0.5 1 5 0.5 0.5 25 (Number Average Particle Size 55 μm) (% by mass)Particles C 1 (Number Average Particle Size 3500 μm) (% by mass)Particles D 99.5 (Number Average Particle Size 1300 μm) (% by mass)Particles E 99.5 (Number Average Particle Size 460 μm) (% by mass)Surface Appearance ◯ ◯ ◯ ◯ ◯ — X — Impact Resistance (kJ/m2) 9 12 10 109 — 4 —

The properties (surface appearance) were rated on the basis of visualobservation of the surface appearance of the thermoplastic resin moldedproduct; a good molded product having no strain or burning was rated as◯, a thermoplastic resin molded product having strain on a part of itssurface was rated as Δ, and a thermoplastic resin molded product havingstrain or a defect was rated as x, and those which could not beevaluated were rated as −.

The mechanical strength (impact resistance) was measured in terms ofcharpy impact strength according to ISO179 (notched, thickness: 3.2 mm).

As a result of visual observation of the surface appearance, theinventions 1 to 5 were rated as ◯, indicating that they are superior ingood surface appearance and impact resistance. On the other hand, thecomparison 2 developed burning, and gave poor results for the surfaceappearance and impact resistance. The reason for this is likely that themixing proportion of the particles B was as high as 25% by mass. Thecomparisons 1 and 3 could not be molded, and thus no rating was givenfor the surface appearance and impact resistance.

These results indicate that the use of the thermoplastic resin particlecomposition 6A containing the large and small thermoplastic resinparticles 61 and 62 described in Example 2 allows molding of thethermoplastic resin molded product 60 having good properties andmechanical strength.

Example 3

The thermoplastic resin particle composition 6A of the present exampleis to be filled into the cavity 22 of the rubber die 2 made of a rubbermaterial, and heated to be melted by irradiation with electromagneticwaves having wavelengths ranging from 0.78 to 2 μm through the rubberdie 2. The thermoplastic resin particle composition 6A contains thethermoplastic resin particles 61 and the fine particles 62 of at leastone of an inorganic powder and a lubricant. The number average particlesize of the thermoplastic resin particles 61 is from 200 to 3000 μm, andthe number average particle size of the fine particles 62 is from 0.5 to50 μm. The thermoplastic resin particle composition 6A of the presentexample contains 0.1 to 10 parts by mass of the fine particles 62 withreference to 100 parts by mass of the thermoplastic resin particles 61.

The thermoplastic resin used in the present example is an ABS resinwhich is a non-crystalline rubber-reinforced styrene resin.

The process for producing the thermoplastic resin molded product 60using the molding machine 1 is describe below in detail with referenceto FIGS. 1 to 3.

In the process of the present example for producing the thermoplasticresin molded product 60, the thermoplastic resin particle composition 6Aand the thermoplastic resin 6B in a molten state are used for moldingthe thermoplastic resin molded product 60 by filling the thermoplasticresin 6 into the rubber die 2. In the present example, the thermoplasticresin particle composition 6A and the thermoplastic resin 6B in a moltenstate are ABS resins having the same constitution.

When the thermoplastic resin molded product 60 is molded, firstly, asthe placement step shown in FIG. 1, the fine particles 62 having avolume average particle size of 0.5 to 50 μm are sprinkled over thesurface of the cavity 22 at the split die 21 of the rubber die 2 in anopened state. Subsequently, the injection cylinder 52 is set in theinlet 23 of the mold, and the thermoplastic resin particles 61 having anumber average particle size of 200 to 3000 μm are charged into thecavity 22 of the rubber die 2. At that time, the thermoplastic resinparticle composition 6A charged into the cavity 22 is composed of 0.1 to10 parts by mass of the fine particles 62 with reference to 100 parts bymass of the thermoplastic resin particle 61. The thermoplastic resinparticle composition 6A is filled into almost the whole of the cavity22.

When the fine particles 62 are sprinkled over the surface of the cavity22, most part of the fine particles 62 adheres to the inner wall surface221 of the cavity 22. The fine particles 62 effectively adhere to theinner wall surface 221 of the cavity 22 made of silicone rubber, becausethe rubber die 2 of the present example is made of silicone rubber, andthe fine particles 62 have a volume average particle size of 0.5 to 50μm.

When the thermoplastic resin particles 61 are charged into the cavity22, the fine particles 62 are adhered to the inner wall surface 221 ofthe cavity 22. As a result of this, the thermoplastic resin particles 61pass (fall) on the inner side of the fine particles 62 in the cavity 22.Therefore, the thermoplastic resin particles 61 are smoothly filled intothe cavity 22. The fine particles 62 and the thermoplastic resinparticles 61 may be filled under their self weights, or using vibrationor air stream.

Subsequently, also in the present example, in the same manner as inExample 2, the vacuum step, particle heating step (see FIG. 2), and thefilling step (see FIG. 3) may be carried out, thereby obtaining thethermoplastic resin molded product 60 having good properties such asappearance, shape, and surface accuracy, and high mechanical strength.

The structure of the molding machine 1 used in the present example isthe same as that used in Example 1, and the structure and effect of theproduction process of the present example are the same as those inExample 2.

(Effect Simulation)

The effect simulation for the use of the thermoplastic resin particles61 and fine particles 62 of the present example is illustrated by, inFIG. 7, replacing the large thermoplastic resin particles 61 of Example2 with the thermoplastic resin particles 61, the small thermoplasticresin particles 62 of Example 2 with the fine particles 62, and, in FIG.8, the large thermoplastic resin particles 61 of Example 2 with thethermoplastic resin particles 61. The present example will achieve thesame effect as Example 2.

(Confirmatory Test 3)

The present confirmatory test examined improvements in properties(surface appearance) and mechanical strength (impact resistance)achieved by the use of the thermoplastic resin particle composition 6Ain Example 3 for the molding of a thermoplastic molded product.

The five types of thermoplastic resin particles (particles A, B, C, D,and E) used in the present confirmatory test are the same as those usedin Example 2. The present confirmatory test used two types of talc (talcA and B), and a lubricant.

(Talc A) Fine powder talc “MICRO ACE K-1” (trade name, manufactured byNippon Talc Co., Ltd.) was used. The volume average particle size (D₅₀)was 8 μm as measured by laser diffractometry.

(Talc B) General-purpose talc “MS” (trade name, manufactured by NipponTalc Co., Ltd.) was used. The volume average particle size (D₅₀) was 14μm as measured by laser diffractometry.

(Lubricant) Magnesium stearate “SM-1000” (manufactured by Sakai ChemicalIndustry Co., Ltd.) was used. The volume average particle size (D₅₀) was9 μm as measured by laser diffractometry.

The number average particle size was measured through the image analysisof micrographs using an image analysis software (“Image Pro Plus”,manufactured by Media Cybernetics Inc.). 100 or more samples weresubjected to image processing.

In the present confirmatory test, a rectangular cavity 22 having a sizeof 125 mm×12.5 mm×3.2 mm was made from silicone rubber. The minimumwidth dimension of the cavity 22 was 3.2 mm. Using the molding machine 1described in Example 1, the particles A, B, C, D, and E wererespectively filled into the cavity 22, and heated to be melted. Athermoplastic resin in a molten state was additionally filled, and thencooled to obtain samples of a thermoplastic resin molded product.

Table 3 lists the results of the observation of surface appearance andthe measurements of the impact resistance of the inventions 1 to 6molded from the thermoplastic resin particle composition 6A composed ofthe particles A, D, and E, and the talc or lubricant, and thecomparisons 1 to 3 molded from the thermoplastic resin particlescomposed of the particles A alone, or the particles B or C.

TABLE 3 Inventions Comparisons 1 2 3 4 5 6 1 2 3 Particles A 100 100 100100 100 (Number Average Particle Size 700 μm) (% by mass) Particles B100 (Number Average Particle Size 550 μm) (% by mass) Particles C 100(Number Average Particle Size 3500 μm) (% by mass) Particles D 100(Number Average Particle Size 1300 μm) (% by mass) Particles E 100(Number Average Particle Size 460 μm) (% by mass) Talc A(8 μm) (Parts byMass) 0.5 1 0.5 0.5 0.5 0.5 Talc B(14 μm) (Parts by Mass) 0.5 Lublicant(9 μm) (Parts by Mass) 0.5 Surface Appearance ◯ ◯ ◯ ◯ ◯ 0 — X — ImpactResistance (kJ/m²) 8 6 7 9 8 7 — 3 —

The properties (surface appearance) were rated on the basis of visualobservation of the surface appearance of the thermoplastic resin moldedproduct; a good molded product having no strain or burning was rated as◯, a thermoplastic resin molded product having strain on a part of itssurface was rated as Δ, and a thermoplastic resin molded product havingstrain or a defect was rated as x, and those which could not beevaluated were rated as −.

The mechanical strength (impact resistance) was measured in terms ofcharpy impact strength according to ISO179 (notched, thickness: 3.2 mm).

As a result of visual observation of the surface appearance, theinventions 1 to 6 were rated as ◯, indicating that they are superior ingood surface appearance and impact resistance. On the other hand, thecomparison 2 developed burning, and gave poor results for the surfaceappearance and impact resistance. The reason for this is likely that thenumber average particle size of the particles B is as small as 55 μm.The comparisons 1 and 3 could not be molded, and thus no rating wasgiven for the surface appearance and impact resistance.

These results indicate that the use of the thermoplastic resin particlecomposition 6A containing the thermoplastic resin particles 61 and thefine particles 62 described in Example 3 allows molding of thethermoplastic resin molded product 60 having good properties andmechanical strength.

Example 4

The thermoplastic resin composition 6A of the present example is to befilled into the cavity 22 of the rubber die 2 made of a rubber material,and heated to be melted by irradiation with electromagnetic waves havingwavelengths ranging from 0.78 to 2 μm through the rubber die 2. Thethermoplastic resin composition 6A contains 0.0005 to 0.1 parts by massof an infrared ray absorbing agent with reference to 100 parts by massof the thermoplastic resin such that the thermoplastic resin moldedproduct 60 has a haze value of 20% or less.

The thermoplastic resin used in the present example is a transparent ABSresin which is a non-crystalline rubber-reinforced styrene resin.

FIG. 9 shows graphs showing the difference of the optical absorptioncoefficient between the thermoplastic resin containing no infrared rayabsorbing agent (indicated with a broken line) and that containing aninfrared ray absorbing agent (indicated with a solid line), taking thewavelength (nm) as abscissa, and the optical absorption coefficient (%)as ordinate. FIG. 9 indicates that the thermoplastic resin compositioncontaining an infrared ray absorbing agent achieves a higher absorptioncoefficient of near-infrared rays having wavelengths from 0.78 to 2 μmthan the thermoplastic resin containing no infrared ray absorbing agent.The thermoplastic resin containing no infrared ray absorbing agentcorresponds to the comparison 1 in the below-described confirmatory test4, and the thermoplastic resin containing an infrared ray absorbingagent corresponds to the invention 2 in the below-described confirmatorytest 4.

In the process of the present example for producing the thermoplasticresin molded product 60, the thermoplastic resin composition 6A and thethermoplastic resin 6B in a molten state are used for molding thethermoplastic resin molded product 60 by filling the thermoplastic resin6 into the rubber die 2. In the present example, the thermoplastic resincomposing the thermoplastic resin composition 6A and the thermoplasticresin 6B in a molten state are ABS resins having the same constitution.The large and small thermoplastic resin particles 61 and 62 used as thethermoplastic resin composition 6A contain an infrared ray absorbingagent in the same proportions.

When the thermoplastic resin molded product 60 is molded, firstly, asthe placement step shown in FIG. 1, the small thermoplastic resinparticles 62 having a particle size of 1 to 100 μm are sprinkled overthe inner wall surface 221 of the cavity 22 at the split die 21 of therubber die 2 in an opened state.

Subsequently, the injection cylinder 52 is set in the inlet 23 of therubber die 2 in a closed state, and the large thermoplastic resinparticles 61 having a particle size of more than 100 μm to 3000 μm orless are charged into the cavity 22 of the rubber die 2. At that time,the thermoplastic resin composition 6A charged into the cavity 22 iscomposed of 80 to 99.9% by mass of the large thermoplastic resinparticles 61, and 0.1 to 20% by mass of the small thermoplastic resinparticles 62. The thermoplastic resin composition 6A is filled intoalmost the whole of the cavity 22.

Subsequently, also in the present example, in the same manner as inExample 2, the vacuum step, particle heating step (see FIG. 2), and thefilling step (see FIG. 3) are carried out, thereby obtaining thethermoplastic resin molded product 60 having good properties such asappearance, shape, and surface accuracy, and high mechanical strength.

In the particle heating step of the present example, the infrared rayabsorbing agent contained in the large thermoplastic resin particles 61allows effective absorption of the electromagnetic waves, in spite ofthe use of the transparent thermoplastic resin, and thus allows quickheating and melting of the thermoplastic resin composition 6A.

Therefore, according to the process of the present example for producingthe thermoplastic resin molded product 60, the addition of an infraredray absorbing agent allows quick molding of the transparentthermoplastic resin molded product 60 having a haze value of 20% orless, which is an index representing the transparency of the resin, byirradiation with electromagnetic waves. In addition, the rubber die 2used for molding is readily made, which allows low-cost production ofthe thermoplastic resin molded product 60 of various shapes.

Further, when the thermoplastic resin 6 is molded using the rubber die2, the transparent thermoplastic resin molded product 60 has effectivelyimproved properties such as appearance, shape, and surface accuracy, andmechanical strength. The present example is markedly effective when thethermoplastic resin molded product 60 to be molded is large orthin-walled, or when the thermoplastic resin 6 used for molding has ahigh viscosity.

The structure of the molding machine 1 used in the present example isthe same as that used in Example 1, and the structure and effect of theproduction process of the present example are the same as those inExample 2.

(Confirmatory Test 4)

The present confirmatory test examined whether or not the addition of aninfrared ray absorbing agent reduces the time taken until thethermoplastic resin composition 6A melts.

Specifically, the resins 1 to 3 as thermoplastic resins containing noinfrared ray absorbing agent were used as the comparisons 1 to 3, andthe thermoplastic resin composition 6A made by adding an infrared rayabsorbing agent to the resins 1 to 3 was used as the inventions 1 to 8.The inventions 1 to 8 and the comparisons 1 to 3 were measured for thetime taken until they melt (in the present confirmatory test, the timetaken until the temperature reached 260° C.) (minute) and the haze value(%) of the molded products. The temperature and time for obtaining themolded products were adjusted as needed.

In the present confirmatory test, the following thermoplastic resins 1to 3 were subjected to the measurements.

(Resin 1) A transparent ABS resin (“TECHNO ABS 830” manufactured byTechno Polymer Co., Ltd., MFR 30 g/10 min (220° C., 98N)), a test piecehaving a thickness of 2.5 mm giving a haze value of 4%.

(Resin 2) An acrylic resin (“ACRYPET VH001” manufactured by MitsubishiRayon Co., Ltd., MFR 2 g/10 min (230° C., 37.3N)), a test piece having athickness of 2.5 mm giving a haze value of 0.2%.

(Resin 3) A polycarbonate resin (“NOVAREX 7020A” manufactured byMitsubishi Engineering-Plastics Corporation, MFR 30 g/10 min (300° C.,11.8N)), a test piece having a thickness of 2.5 mm giving a haze valueof 0.4%.

The infrared ray absorbing agent was “Lumogen IR1050” manufactured byBASF.

Table 4 lists the constitutions of the inventions 1 to 8 and thecomparisons 1 to 3, and their measurements of the melting time (minute)and the whiteness value (%).

TABLE 4 Inventions Comparisons 1 2 3 4 5 6 7 8 1 2 3 Resin 1 (Parts 100100 100 100 Resin 2 by Mass) 100 100 100 100 100 Resin 3 100 100Infrared Ray Absorbing Agent 0.005 0.01 0.05 0.005 0.01 0.03 0.05 0.01Haze Value (%) 7 9 17 3 5 9 15 5 4 0.2 0.4 Melting Time (Minutes) 16 126 15 12 6 5 11 30 31 35 (Time required for reaching 260° C.)

The inventions 1 to 8 were made as follows. An infrared ray absorbingagent was added to the resins 1 to 3 in the proportions listed in Table4, and the mixture was extruded using a single screw extruder (diameter:40 mm, cylinder temperature: 220 to 260° C.), to form transparentthermoplastic resin particles. From the transparent thermoplastic resinparticles, thermoplastic resin particles having a number averageparticle size of 700 μm were made using an extruder equipped with astrand cutter (for micropellets) manufactured by Gala Industries, Inc.The thermoplastic resin particles had a bulk density of 0.63 g/cm³ asmeasured according to JIS K7365.

The comparisons 1 to 3 were made by forming the resins 1 to 3 containingno infrared ray absorbing agent into thermoplastic resin particleshaving a number average particle size of 700 μm in the same manner asdescribed above.

The cavity 22 of the rubber die 2 made of silicone rubber was made inthe form of a rectangle having a length of 80 mm, a width of 55 mm, anda thickness of 2.5 mm, and heated with a halogen heater. The time takenuntil the normal temperature reached 260° C. (melting time) wasmeasured.

In the present confirmatory test, the haze value was determined bymeasuring a test piece (molded product) having a length of 80 mm, awidth of 55 cm, and a thickness of 2.5 mm with a haze meter (Haze-GardPlus, manufactured by Gardner) according to JIS K7136. The smaller thehaze value is, the higher the transparency is.

Table 4 indicates that the thermoplastic resin composition 6A containingan infrared ray absorbing agent achieves a higher haze value than thethermoplastic resin containing no infrared ray absorbing agent. On theother hand, those containing an infrared ray absorbing agent (theinventions 1 to 8) achieve markedly shorter melting time than thosecontaining no infrared ray absorbing agent (comparisons 1 to 3). Thehigher the proportion of the infrared ray absorbing agent is, theshorter the melting time is. On the other hand, the higher theproportion of the infrared ray absorbing agent is, the greater the hazevalue is, and the lower the transparency is.

The above results suggest that the addition of an infrared ray absorbingagent to the thermoplastic resin allows reduction of the time takenuntil the thermoplastic resin melts, and the quick molding of thethermoplastic resin molded product 60 having a haze value of 20% orless.

Example 5

The thermoplastic resin composition 6A of the present example is to befilled into the cavity 22 of the rubber die 2 made of a rubber material,and heated to be melted by irradiation with electromagnetic waves havingwavelengths ranging from 0.78 to 2 μm through the rubber die 2. Thethermoplastic resin composition 6A contains 0.0005 to 0.1 parts by massof an infrared ray absorbing agent, and 0.05 to 30 parts by mass of acoloring agent with reference to 100 parts by mass of the thermoplasticresin such that the thermoplastic resin molded product 60 has awhiteness value of 30% or more.

The thermoplastic resin used in the present example is an ABS resinwhich is a non-crystalline rubber-reinforced styrene resin.

FIG. 10 shows graphs showing the difference of the optical absorptioncoefficient between the thermoplastic resin containing no infrared ray(indicated with a broken line) and that containing an infrared rayabsorbing agent (indicated with solid and dashed lines), taking thewavelength (nm) as abscissa, and the optical absorption coefficient (%)as ordinate. FIG. 10 indicates that the thermoplastic resin compositioncontaining an infrared ray absorbing agent achieves a higher absorptioncoefficient of near-infrared rays having wavelengths from 0.78 to 2 μmthan the thermoplastic resin containing no infrared ray absorbing agent.The thermoplastic resin containing no infrared ray absorbing agentcorresponds to the comparison 1 in the below-described confirmatory test5, and the thermoplastic resin containing an infrared ray absorbingagent corresponds to the invention 1 (containing a small amount of aninfrared ray absorbing agent) and the invention 2 (containing a largeamount of an infrared ray absorbing agent) in the below-describedconfirmatory test 5.

In the process of the present example for producing the thermoplasticresin molded product 60, in the same manner as in Example 4, the vacuumstep, the particle heating step (see FIG. 2), and the filling step (seeFIG. 3) are carried out, thereby obtaining the thermoplastic resinmolded product 60 having good properties such as appearance, shape, andsurface accuracy, and high mechanical strength.

In addition, in the production process of the present example, the largeand small thermoplastic resin particles 61 and 62 used as thethermoplastic resin composition 6A contain an infrared ray absorbingagent and a coloring agent in the same proportions. In the large andsmall thermoplastic resin particles 61 and 62 and the thermoplasticresin 6B in a molten state, the proportion of the coloring agent is from0.05 to 30 parts by mass with reference to 100 parts by mass of thethermoplastic resin 6B.

Therefore, according to the process of the present example for producingthe thermoplastic resin molded product 60, the addition of an infraredray absorbing agent and a coloring agent allows quick molding of thethermoplastic resin molded product 60 having a whiteness value of 30% ormore by irradiation with electromagnetic waves. In addition, the rubberdie 2 used for molding is readily made, which allows low-cost productionof the thermoplastic resin molded product 60 of various shapes.

The structure of the molding machine 1 used in the present example isthe same as that used in Example 1, and the structure and effect of theproduction process of the present example are the same as those inExample 4.

(Confirmatory Rest 5)

The present confirmatory test examined whether or not the addition of aninfrared ray absorbing agent reduces the time taken until thethermoplastic resin composition 6A melts.

Specifically, the resins 1 and 2 as thermoplastic resins containing noinfrared ray absorbing agent were used as the comparisons 1 to 3, andthe thermoplastic resin composition 6A made by adding an infrared rayabsorbing agent to the resins 1 and 2 was used as the inventions 1 to 4.The inventions 1 to 4 and the comparisons 1 to 3 were measured for thetime taken until they melt (in the present confirmatory test, the timetaken until the temperature reached 260° C.) (minute) and the whitenessvalue (%) of the molded products.

In the present confirmatory test, the following thermoplastic resins 1and 2 were subjected to the measurements.

(Resin 1) A transparent ABS resin (“TECHNO ABS 830” manufactured byTechno Polymer Co., Ltd., MFR 30 g/10 min (220° C., 98N)), a test piecehaving a thickness of 2.5 mm giving a whiteness value of 97%.

(Resin 2) An ABS resin (“TECHNO ABS 330” manufactured by Techno PolymerCo., Ltd., MFR 42 g/10 min (220° C., 98N)), a test piece having athickness of 2.5 mm giving a whiteness value of 34%.

The infrared ray absorbing agent was “Lumogen IR1050” manufactured byBASF.

In the confirmatory test, the following coloring agents 1 to 3 wereused.

(Coloring agent 1) White, titanium oxide (“TIPAQUE CR-6-2” manufacturedby Ishihara Sangyo Kaisha, Ltd.).

(Coloring agent 2) Green, (“AM110 GREEN, manufactured by KawamuraChemical Co., Ltd.).

(Coloring agent 3) Black, (“MB-9705 BLACK”, manufactured by KoshigayaKasei Co., Ltd.).

Table 5 lists the constitutions of the inventions 1 to 4 and thecomparisons 1 to 3, and their measurements of the melting time (minute)and the whiteness value (%).

TABLE 5 Inventions Comparisons 1 2 3 4 1 2 3 Resin 1 (Parts 100 100 100100 100 Resin 2 by Mass) 100 100 Infrared Ray Absorbing Agent 0.01 0.050.01 0.01 Coloring Agent 1(White) 3 3 3 3 Coloring Agent 2(Green) 1 1Coloring Agent 3(Black) 1 Whiteness Value (%) 89 78 33 87 97 34 22Melting Time (Minutes) 17 12 8 15 31 22 5 (Time required for reaching260° C.)

The inventions 1 to 4 were made as follows. An infrared ray absorbingagent and coloring agent were added to the resins 1 and 2 in theproportions listed in Table 5, and the mixture was extruded using asingle screw extruder (diameter: 40 mm, cylinder temperature: 220 to260° C.), to form colored thermoplastic resin particles. From thecolored thermoplastic resin particles, thermoplastic resin particleshaving a number average particle size of 700 μm were made using anextruder equipped with a strand cutter (for micropellets) manufacturedby Gala Industries, Inc. The thermoplastic resin particles had a bulkdensity of 0.63 g/cm³ as measured according to JIS K7365.

The comparisons 1 to 3 were made by adding the coloring agents in theproportions listed in Table 5 to the resins 1 and 2, and forming theminto thermoplastic resin particles having a number average particle sizeof 700 μm in the same manner as described above.

The cavity 22 of the rubber die 2 made of silicone rubber was made inthe form of a rectangle having a length of 80 mm, a width of 55 mm, anda thickness of 2.5 mm, and heated with a halogen heater. The time takenuntil the normal temperature reached 260° C. (melting time) wasmeasured.

In the present confirmatory test, the whiteness was determined bymeasuring the L, a, and b of a test piece (molded product) having alength of 80 mm, a width of 55 cm, and a thickness of 2.5 mm using aHunter color difference meter, and calculated from the formula:

W(%)=100−{(100−L)² +a ² +b ²}^(1/2)

wherein L is brightness, a is redness, and b is yellowness. The higherthe whiteness value is, the closer to white the test piece is.

Table 5 indicates that the thermoplastic resin composition 6A containingan infrared ray absorbing agent achieves a lower whiteness value thanthe thermoplastic resin containing no infrared ray absorbing agent. Onthe other hand, those containing an infrared ray absorbing agent (theinventions 1 to 4) achieve markedly shorter melting time than thosecontaining no infrared ray absorbing agent (comparisons 1 to 3). Thehigher the proportion of the infrared ray absorbing agent is, theshorter the melting time is. On the other hand, the higher theproportion of the infrared ray absorbing agent is, the lower thewhiteness value is.

The above results suggest that the addition of an infrared ray absorbingagent to the thermoplastic resin allows reduction of the time takenuntil the thermoplastic resin melts, and the quick molding of thethermoplastic resin molded product 60 having a whiteness of 30% or more.

1. A process, comprising: irradiating a thermoplastic resin particlecomposition present in a cavity of a rubber die comprised of a rubbermaterial with electromagnetic waves having wavelengths ranging from 0.78to 2 μm through the rubber die, thereby heating to melt thethermoplastic resin particle composition; and cooling a thermoplasticresin in the cavity thereby obtaining a thermoplastic resin moldedproduct.
 2. The process of claim 1, further comprising: filling athermoplastic resin in a molten state into a space left in the cavity,which is carried out after said irradiating and before said cooling. 3.The process of claim 2, wherein, during said filling, the thermoplasticresin in a molten state is filled into the space left in the cavityunder an injection pressure of 0.5 to 5 MPa.
 4. A process, comprising:irradiating a thermoplastic resin particle composition present in acavity of a rubber die comprised of a rubber material withelectromagnetic waves having wavelengths ranging from 0.78 to 2 μmthrough the rubber die, thereby heating to melt the thermoplastic resinparticle composition; cooling a thermoplastic resin in the cavitythereby obtaining a thermoplastic resin molded product; and vacuumingthe cavity or the space left in the cavity, wherein the thermoplasticresin particle composition is present in the entirety of the cavity or aspace is present in the cavity, and said vacuuming is carried out atleast before said irradiating is carried out.
 5. A process, comprising:irradiating a thermoplastic resin particle composition present in acavity of a rubber die comprised of a rubber material withelectromagnetic waves having wavelengths ranging from 0.78 to 2 μmthrough the rubber die, thereby heating to melt the thermoplastic resinparticle composition; and cooling a thermoplastic resin in the cavitythereby obtaining a thermoplastic resin molded product, wherein the bulkdensity of the thermoplastic resin particle composition is 0.4 g/cm³ ormore.
 6. (canceled)
 7. The process of claim 1, wherein the thermoplasticresin particle composition comprises thermoplastic resin particles andfine particles of at least one of an inorganic powder and a lubricant,the number average particle size of the thermoplastic resin particlesbeing from 200 to 3000 μm, the volume average particle size of the fineparticles being from 0.5 to 50 μm, and the content of the fine particlesbeing from 0.1 to 10 parts by mass with reference to 100 parts by massof the thermoplastic resin particles.
 8. The process of claim 1, whereinthe thermoplastic resin particle composition comprises 0.0005 to 0.1parts by mass of an infrared ray absorbing agent with reference to 100parts by mass of the thermoplastic resin particles.
 9. The process ofclaim 1, wherein the thermoplastic resin particle composition is arubber-reinforced styrene resin.
 10. A thermoplastic resin moldedproduct obtained by the process of claim
 1. 11-14. (canceled)
 15. Aprocess, comprising: irradiating a thermoplastic resin particlecomposition present in a cavity of a rubber die comprised of a rubbermaterial with electromagnetic waves having wavelengths ranging from 0.78to 2 μm through the rubber die, thereby heating to melt thethermoplastic resin particle composition; cooling a thermoplastic resinin the cavity thereby obtaining a thermoplastic resin molded product;and vacuuming the cavity or the space left in the cavity, wherein thethermoplastic resin particle composition is present in the entirety ofthe cavity or a space is present in the cavity, said vacuuming iscarried out at least before said irradiating is carried out, and whereinthe bulk density of the thermoplastic resin particle composition is 0.4g/cm³ or more.
 16. The process of claim 4, wherein the thermoplasticresin particle composition comprises thermoplastic resin particles andfine particles of at least one of an inorganic powder and a lubricant,the number average particle size of the thermoplastic resin particlesbeing from 200 to 3000 μm, the volume average particle size of the fineparticles being from 0.5 to 50 μm, and the content of the fine particlesbeing from 0.1 to 10 parts by mass with reference to 100 parts by massof the thermoplastic resin particles.
 17. The process of claim 5 whereinthe thermoplastic resin particle composition comprises thermoplasticresin particles and fine particles of at least one of an inorganicpowder and a lubricant, the number average particle size of thethermoplastic resin particles being from 200 to 3000 μm, the volumeaverage particle size of the fine particles being from 0.5 to 50 μm, andthe content of the fine particles being from 0.1 to 10 parts by masswith reference to 100 parts by mass of the thermoplastic resinparticles.
 18. The process of claim 15 wherein the thermoplastic resinparticle composition comprises thermoplastic resin particles and fineparticles of at least one of an inorganic powder and a lubricant, thenumber average particle size of the thermoplastic resin particles beingfrom 200 to 3000 μm, the volume average particle size of the fineparticles being from 0.5 to 50 μm, and the content of the fine particlesbeing from 0.1 to 10 parts by mass with reference to 100 parts by massof the thermoplastic resin particles.
 19. The process of claim 4,wherein the thermoplastic resin particle composition comprises 0.0005 to0.1 parts by mass of an infrared ray absorbing agent with reference to100 parts by mass of the thermoplastic resin particles.
 20. The processof claim 5, wherein the thermoplastic resin particle compositioncomprises 0.0005 to 0.1 parts by mass of an infrared ray absorbing agentwith reference to 100 parts by mass of the thermoplastic resinparticles.
 21. The process of claim 15, wherein the thermoplastic resinparticle composition comprises 0.0005 to 0.1 parts by mass of aninfrared ray absorbing agent with reference to 100 parts by mass of thethermoplastic resin particles.
 22. A thermoplastic resin molded productobtained by the process of claim
 4. 23. A thermoplastic resin moldedproduct obtained by the process of claim
 5. 24. A thermoplastic resinmolded product obtained by the process of claim 15.